diff --git a/src/modules/module-avb/maap.c b/src/modules/module-avb/maap.c
index 866d234c9..b66eb9437 100644
--- a/src/modules/module-avb/maap.c
+++ b/src/modules/module-avb/maap.c
@@ -4,7 +4,7 @@
 
 #include <unistd.h>
 
-#include <spa/utils/json.h>
+#include <spa/utils/json-builder.h>
 
 #include <pipewire/pipewire.h>
 
@@ -298,23 +298,26 @@ static int load_state(struct maap *maap)
 
 static int save_state(struct maap *maap)
 {
+	struct spa_json_builder b;
 	char *ptr;
 	size_t size;
-	FILE *f;
 	char key[512];
 	uint32_t count;
+	int res;
 
-	if ((f = open_memstream(&ptr, &size)) == NULL)
-		return -errno;
+	if ((res = spa_json_builder_memstream(&b, &ptr, &size, 0)) < 0)
+		return res;
 
-	fprintf(f, "[ ");
-	fprintf(f, "{ \"start\": \"%02x:%02x:%02x:%02x:%02x:%02x\", ",
+	spa_json_builder_array_push(&b, "[");
+	spa_json_builder_array_push(&b,   "{");
+	spa_json_builder_object_stringf(&b, "start", "%02x:%02x:%02x:%02x:%02x:%02x",
 			maap_base[0], maap_base[1], maap_base[2],
 			maap_base[3], (maap->offset >> 8) & 0xff,
 			maap->offset & 0xff);
-	fprintf(f, " \"count\": %u } ", maap->count);
-	fprintf(f, "]");
-	fclose(f);
+	spa_json_builder_object_uint(&b,    "count", maap->count);
+	spa_json_builder_pop(&b,          "}");
+	spa_json_builder_pop(&b,        "]");
+	spa_json_builder_close(&b);
 
 	count = pw_properties_set(maap->props, "maap.addresses", ptr);
 	free(ptr);
diff --git a/src/modules/module-jackdbus-detect.c b/src/modules/module-jackdbus-detect.c
index 622ca6efe..11ad5bdb3 100644
--- a/src/modules/module-jackdbus-detect.c
+++ b/src/modules/module-jackdbus-detect.c
@@ -17,6 +17,7 @@
 
 #include <spa/utils/string.h>
 #include <spa/utils/result.h>
+#include <spa/utils/json-builder.h>
 #include <spa/support/dbus.h>
 #include <spa-private/dbus-helpers.h>
 
@@ -116,22 +117,21 @@ static const struct pw_impl_module_events tunnelmodule_events = {
 
 static int load_jack_tunnel(struct impl *impl)
 {
-	FILE *f;
+	struct spa_json_builder b;
 	char *args;
 	size_t size;
 	int res = 0;
 
-	if ((f = open_memstream(&args, &size)) == NULL) {
-		res = -errno;
+	if ((res = spa_json_builder_memstream(&b, &args, &size, 0)) < 0) {
 		pw_log_error("Can't open memstream: %m");
 		goto done;
 	}
 
-	fprintf(f, "{");
+	spa_json_builder_array_push(&b, "{");
 	if (impl->properties != NULL)
-		pw_properties_serialize_dict(f, &impl->properties->dict, 0);
-	fprintf(f, " }");
-	fclose(f);
+		pw_properties_serialize_dict(b.f, &impl->properties->dict, 0);
+	spa_json_builder_pop(&b,        "}");
+	spa_json_builder_close(&b);
 
 	pw_log_info("loading module args:'%s'", args);
 	impl->jack_tunnel = pw_context_load_module(impl->context,
diff --git a/src/modules/module-parametric-equalizer.c b/src/modules/module-parametric-equalizer.c
index d0f2885ef..9f0ef7247 100644
--- a/src/modules/module-parametric-equalizer.c
+++ b/src/modules/module-parametric-equalizer.c
@@ -9,7 +9,7 @@
 #include <limits.h>
 
 #include <spa/utils/result.h>
-#include <spa/utils/json-core.h>
+#include <spa/utils/json-builder.h>
 #include <spa/param/audio/raw.h>
 
 #include <pipewire/impl.h>
@@ -162,7 +162,7 @@ static const struct pw_impl_module_events filter_chain_module_events = {
 
 static int enhance_properties(struct pw_properties *props, const char *key, ...)
 {
-	FILE *f;
+	struct spa_json_builder b;
 	spa_autoptr(pw_properties) p = NULL;
 	char *args = NULL;
 	const char *str;
@@ -187,13 +187,12 @@ static int enhance_properties(struct pw_properties *props, const char *key, ...)
         }
         va_end(varargs);
 
-	if ((f = open_memstream(&args, &size)) == NULL) {
-		res = -errno;
+	if ((res = spa_json_builder_memstream(&b, &args, &size, 0)) < 0) {
 		pw_log_error("Can't open memstream: %m");
 		return res;
 	}
-	pw_properties_serialize_dict(f, &p->dict, PW_PROPERTIES_FLAG_ENCLOSE);
-	fclose(f);
+	pw_properties_serialize_dict(b.f, &p->dict, PW_PROPERTIES_FLAG_ENCLOSE);
+	spa_json_builder_close(&b);
 
 	pw_properties_set(props, key, args);
 	free(args);
@@ -202,12 +201,11 @@ static int enhance_properties(struct pw_properties *props, const char *key, ...)
 
 static int create_eq_filter(struct impl *impl, const char *filename)
 {
-	FILE *f = NULL;
+	struct spa_json_builder b;
 	const char* str;
 	char *args = NULL;
 	size_t size;
 	int32_t res = 0;
-	char path[PATH_MAX];
 
 	if ((str = pw_properties_get(impl->props, "equalizer.description")) != NULL) {
 		if (pw_properties_get(impl->props, PW_KEY_NODE_DESCRIPTION) == NULL)
@@ -216,47 +214,47 @@ static int create_eq_filter(struct impl *impl, const char *filename)
 			pw_properties_set(impl->props, PW_KEY_MEDIA_NAME, str);
 	}
 
-	spa_json_encode_string(path, sizeof(path), filename);
-	pw_properties_setf(impl->props, "filter.graph",
-			"{"
-			"  nodes = [ "
-			"    { type = builtin name = eq label = param_eq "
-			"      config = { filename = %s } "
-			"    } "
-			"  ] "
-			"}", path);
-
 	enhance_properties(impl->props, "capture.props", PW_KEY_MEDIA_CLASS, "Audio/Sink", NULL);
 	enhance_properties(impl->props, "playback.props", PW_KEY_NODE_PASSIVE, "true", NULL);
 
-	if ((f = open_memstream(&args, &size)) == NULL) {
-		res = -errno;
+	if ((res = spa_json_builder_memstream(&b, &args, &size, 0)) < 0) {
 		pw_log_error("Can't open memstream: %m");
-		goto done;
+		return res;
 	}
-	pw_properties_serialize_dict(f, &impl->props->dict, PW_PROPERTIES_FLAG_ENCLOSE);
-	fclose(f);
+
+	spa_json_builder_array_push(&b, "{");
+	spa_json_builder_object_push(&b,  "filter.graph", "{");
+	spa_json_builder_object_push(&b,    "nodes", "[");
+	spa_json_builder_array_push(&b,       "{");
+	spa_json_builder_object_string(&b,      "type", "builtin");
+	spa_json_builder_object_string(&b,      "name", "eq");
+	spa_json_builder_object_string(&b,      "label", "param_eq");
+	spa_json_builder_object_push(&b,        "config", "{");
+	spa_json_builder_object_string(&b,        "filename", filename);
+	spa_json_builder_pop(&b,                "}");
+	spa_json_builder_pop(&b,              "}");
+	spa_json_builder_pop(&b,            "]");
+	spa_json_builder_pop(&b,          "}");
+	pw_properties_serialize_dict(b.f, &impl->props->dict, 0);
+	spa_json_builder_pop(&b,        "}");
+	spa_json_builder_close(&b);
 
 	pw_log_info("loading new module-filter-chain with args: %s", args);
 	impl->eq_module = pw_context_load_module(impl->context,
 				"libpipewire-module-filter-chain",
 				args, NULL);
+	free(args);
+
 	if (!impl->eq_module) {
-		res = -errno;
 		pw_log_error("Can't load module: %m");
-		goto done;
+		return -errno;
 	}
 	pw_log_info("loaded new module-filter-chain");
 
 	pw_impl_module_add_listener(impl->eq_module,
 			&impl->eq_module_listener,
 			&filter_chain_module_events, impl);
-
-	res = 0;
-
-done:
-	free(args);
-	return res;
+	return 0;
 }
 
 static void core_error(void *data, uint32_t id, int seq, int res, const char *message)
diff --git a/src/modules/module-protocol-pulse/format.c b/src/modules/module-protocol-pulse/format.c
index 99e8919c7..56f164469 100644
--- a/src/modules/module-protocol-pulse/format.c
+++ b/src/modules/module-protocol-pulse/format.c
@@ -8,7 +8,7 @@
 #include <spa/param/audio/format-utils.h>
 #include <spa/param/audio/raw.h>
 #include <spa/param/audio/raw-json.h>
-#include <spa/utils/json.h>
+#include <spa/utils/json-builder.h>
 
 #include "format.h"
 
@@ -703,18 +703,19 @@ static int add_int(struct format_info *info, const char *k, struct spa_pod *para
 		break;
 	case SPA_CHOICE_Enum:
 	{
+		struct spa_json_builder b;
 		char *ptr;
 		size_t size;
-		FILE *f;
+		int res;
 
-		if ((f = open_memstream(&ptr, &size)) == NULL)
-			return -errno;
+		if ((res = spa_json_builder_memstream(&b, &ptr, &size, 0)) < 0)
+			return res;
 
-		fprintf(f, "[");
+		spa_json_builder_array_push(&b, "[");
 		for (i = 1; i < n_values; i++)
-			fprintf(f, "%s %d", i == 1 ? "" : ",", values[i]);
-		fprintf(f, " ]");
-		fclose(f);
+			spa_json_builder_array_int(&b, values[i]);
+		spa_json_builder_pop(&b, "]");
+		spa_json_builder_close(&b);
 
 		pw_properties_set(info->props, k, ptr);
 		free(ptr);
diff --git a/src/modules/module-protocol-pulse/modules/module-always-sink.c b/src/modules/module-protocol-pulse/modules/module-always-sink.c
index f51c39df8..a57c263af 100644
--- a/src/modules/module-protocol-pulse/modules/module-always-sink.c
+++ b/src/modules/module-protocol-pulse/modules/module-always-sink.c
@@ -2,7 +2,7 @@
 /* SPDX-FileCopyrightText: Copyright © 2022 Wim Taymans <wim.taymans@gmail.com> */
 /* SPDX-License-Identifier: MIT */
 
-#include <spa/utils/json.h>
+#include <spa/utils/json-builder.h>
 #include <pipewire/pipewire.h>
 
 #include "../module.h"
@@ -48,22 +48,20 @@ static const struct pw_impl_module_events module_events = {
 static int module_always_sink_load(struct module *module)
 {
 	struct module_always_sink_data *data = module->user_data;
-	FILE *f;
+	struct spa_json_builder b;
 	char *args;
 	const char *str;
-	char encoded[1024];
 	size_t size;
+	int res;
 
-	if ((f = open_memstream(&args, &size)) == NULL)
-		return -errno;
+	if ((res = spa_json_builder_memstream(&b, &args, &size, 0)) < 0)
+		return res;
 
-	fprintf(f, "{");
-	if ((str = pw_properties_get(module->props, "sink_name")) != NULL) {
-		spa_json_encode_string(encoded, sizeof(encoded), str);
-		fprintf(f, " sink.name = %s", encoded);
-	}
-	fprintf(f, " }");
-	fclose(f);
+	spa_json_builder_array_push(&b, "{");
+	if ((str = pw_properties_get(module->props, "sink_name")) != NULL)
+		spa_json_builder_object_string(&b, "sink.name", str);
+	spa_json_builder_pop(&b, "}");
+	spa_json_builder_close(&b);
 
 	data->mod = pw_context_load_module(module->impl->context,
 			"libpipewire-module-fallback-sink",
diff --git a/src/modules/module-protocol-pulse/modules/module-combine-sink.c b/src/modules/module-protocol-pulse/modules/module-combine-sink.c
index b19d0b552..809dd7bd0 100644
--- a/src/modules/module-protocol-pulse/modules/module-combine-sink.c
+++ b/src/modules/module-protocol-pulse/modules/module-combine-sink.c
@@ -5,6 +5,7 @@
 
 #include <spa/param/audio/format-utils.h>
 #include <spa/utils/json.h>
+#include <spa/utils/json-builder.h>
 
 #include <pipewire/pipewire.h>
 #include <pipewire/utils.h>
@@ -155,8 +156,9 @@ static const struct pw_impl_module_events module_events = {
 static int module_combine_sink_load(struct module *module)
 {
 	struct module_combine_sink_data *data = module->user_data;
+	struct spa_json_builder b;
 	uint32_t i;
-	FILE *f;
+	int res;
 	char *args;
 	size_t size;
 
@@ -169,33 +171,41 @@ static int module_combine_sink_load(struct module *module)
 	pw_properties_setf(data->stream_props, "pulse.module.id", "%u",
 			module->index);
 
-	if ((f = open_memstream(&args, &size)) == NULL)
-		return -errno;
+	if ((res = spa_json_builder_memstream(&b, &args, &size, 0)) < 0)
+		return res;
 
-	fprintf(f, "{");
-	pw_properties_serialize_dict(f, &data->props->dict, 0);
-	fprintf(f, " combine.props = {");
-	pw_properties_serialize_dict(f, &data->combine_props->dict, 0);
-	fprintf(f, " } stream.props = {");
-	pw_properties_serialize_dict(f, &data->stream_props->dict, 0);
-	fprintf(f, " } stream.rules = [");
+	spa_json_builder_array_push(&b, "{");
+	pw_properties_serialize_dict(b.f, &data->props->dict, 0);
+	spa_json_builder_object_push(&b,  "combine.props", "{");
+	pw_properties_serialize_dict(b.f, &data->combine_props->dict, 0);
+	spa_json_builder_pop(&b,          "}");
+	spa_json_builder_object_push(&b,  "stream.props", "{");
+	pw_properties_serialize_dict(b.f, &data->stream_props->dict, 0);
+	spa_json_builder_pop(&b,          "}");
+	spa_json_builder_object_push(&b,  "stream.rules", "[");
+	spa_json_builder_array_push(&b,     "{");
+	spa_json_builder_object_push(&b,       "matches", "[");
 	if (data->sink_names == NULL) {
-		fprintf(f, "  { matches = [ { media.class = \"Audio/Sink\" } ]");
-		fprintf(f, "    actions = { create-stream = { } } }");
+		spa_json_builder_array_push(&b,  "{");
+		spa_json_builder_object_string(&b, "media.class", "Audio/Sink");
+		spa_json_builder_pop(&b,         "}");
 	} else {
 		for (i = 0; data->sink_names[i] != NULL; i++) {
-			char name[1024];
-			if (spa_json_encode_string(name, sizeof(name), data->sink_names[i]) >= (int)sizeof(name))
-				continue;
-
-			fprintf(f, "  { matches = [ { media.class = \"Audio/Sink\" ");
-			fprintf(f, " node.name = %s } ]", name);
-			fprintf(f, "    actions = { create-stream = { } } }");
+			spa_json_builder_array_push(&b,  "{");
+			spa_json_builder_object_string(&b, "media.class", "Audio/Sink");
+			spa_json_builder_object_string(&b, "node.name", data->sink_names[i]);
+			spa_json_builder_pop(&b,         "}");
 		}
 	}
-	fprintf(f, " ]");
-	fprintf(f, "}");
-	fclose(f);
+	spa_json_builder_pop(&b,               "]");
+	spa_json_builder_object_push(&b,       "actions", "{");
+	spa_json_builder_object_push(&b,         "create-stream", "{");
+	spa_json_builder_pop(&b,                 "}");
+	spa_json_builder_pop(&b,               "}");
+	spa_json_builder_pop(&b,             "}");
+	spa_json_builder_pop(&b,          "]");
+	spa_json_builder_pop(&b,        "}");
+	spa_json_builder_close(&b);
 
 	data->mod = pw_context_load_module(module->impl->context,
 			"libpipewire-module-combine-stream",
diff --git a/src/modules/module-protocol-pulse/modules/module-echo-cancel.c b/src/modules/module-protocol-pulse/modules/module-echo-cancel.c
index b3a11c339..ee1eb1671 100644
--- a/src/modules/module-protocol-pulse/modules/module-echo-cancel.c
+++ b/src/modules/module-protocol-pulse/modules/module-echo-cancel.c
@@ -5,7 +5,7 @@
 
 #include <spa/param/audio/format-utils.h>
 #include <spa/utils/hook.h>
-#include <spa/utils/json.h>
+#include <spa/utils/json-builder.h>
 #include <pipewire/pipewire.h>
 
 #include "../defs.h"
@@ -87,33 +87,38 @@ static const struct pw_impl_module_events module_events = {
 static int module_echo_cancel_load(struct module *module)
 {
 	struct module_echo_cancel_data *data = module->user_data;
-	FILE *f;
+	struct spa_json_builder b;
 	char *args;
 	size_t size;
+	int res;
 
 	pw_properties_setf(data->capture_props, "pulse.module.id", "%u", module->index);
 	pw_properties_setf(data->source_props, "pulse.module.id", "%u", module->index);
 	pw_properties_setf(data->sink_props, "pulse.module.id", "%u", module->index);
 	pw_properties_setf(data->playback_props, "pulse.module.id", "%u", module->index);
 
-	if ((f = open_memstream(&args, &size)) == NULL)
-		return -errno;
+	if ((res = spa_json_builder_memstream(&b, &args, &size, 0)) < 0)
+		return res;
 
-	fprintf(f, "{");
-	pw_properties_serialize_dict(f, &data->global_props->dict, 0);
-	fprintf(f, " aec.args = {");
-	pw_properties_serialize_dict(f, &data->props->dict, 0);
-	fprintf(f, " }");
-	fprintf(f, " capture.props = {");
-	pw_properties_serialize_dict(f, &data->capture_props->dict, 0);
-	fprintf(f, " } source.props = {");
-	pw_properties_serialize_dict(f, &data->source_props->dict, 0);
-	fprintf(f, " } sink.props = {");
-	pw_properties_serialize_dict(f, &data->sink_props->dict, 0);
-	fprintf(f, " } playback.props = {");
-	pw_properties_serialize_dict(f, &data->playback_props->dict, 0);
-	fprintf(f, " } }");
-	fclose(f);
+	spa_json_builder_array_push(&b, "{");
+	pw_properties_serialize_dict(b.f, &data->global_props->dict, 0);
+	spa_json_builder_object_push(&b, "aec.args", "{");
+	pw_properties_serialize_dict(b.f, &data->props->dict, 0);
+	spa_json_builder_pop(&b, "}");
+	spa_json_builder_object_push(&b, "capture.props", "{");
+	pw_properties_serialize_dict(b.f, &data->capture_props->dict, 0);
+	spa_json_builder_pop(&b, "}");
+	spa_json_builder_object_push(&b, "source.props", "{");
+	pw_properties_serialize_dict(b.f, &data->source_props->dict, 0);
+	spa_json_builder_pop(&b, "}");
+	spa_json_builder_object_push(&b, "sink.props", "{");
+	pw_properties_serialize_dict(b.f, &data->sink_props->dict, 0);
+	spa_json_builder_pop(&b, "}");
+	spa_json_builder_object_push(&b, "playback.props", "{");
+	pw_properties_serialize_dict(b.f, &data->playback_props->dict, 0);
+	spa_json_builder_pop(&b, "}");
+	spa_json_builder_pop(&b, "}");
+	spa_json_builder_close(&b);
 
 	data->mod = pw_context_load_module(module->impl->context,
 			"libpipewire-module-echo-cancel",
@@ -176,40 +181,41 @@ static int parse_point(const char **point, float f[3])
 static int rename_geometry(struct pw_properties *props, const char *pa_key, const char *pw_key)
 {
 	const char *str;
-	int i = 0, len;
+	int i = 0, len, res;
 	char *args;
 	size_t size;
-	FILE *f;
+	struct spa_json_builder b;
 
 	if ((str = pw_properties_get(props, pa_key)) == NULL)
 		return 0;
 
 	pw_log_info("geometry: %s", str);
 
-	if ((f = open_memstream(&args, &size)) == NULL)
-		return -errno;
+	if ((res = spa_json_builder_memstream(&b, &args, &size, 0)) < 0)
+		return res;
 
-	fprintf(f, "[");
+	spa_json_builder_array_push(&b, "[");
 	while (true) {
 		float p[3];
-		char ps0[64], ps1[64], ps2[64];
 		if ((len = parse_point(&str, p)) < 0)
 			break;
 
 		pw_log_info("Got mic #%d position: (%g, %g, %g)", i, p[0], p[1], p[2]);
 
-		fprintf(f, "%s [ %s, %s, %s ]", i == 0 ?  "" : ",",
-				spa_dtoa(ps0, sizeof(ps0), p[0]),
-				spa_dtoa(ps1, sizeof(ps1), p[1]),
-				spa_dtoa(ps2, sizeof(ps2), p[2]));
+		spa_json_builder_array_push(&b, "[");
+		spa_json_builder_array_double(&b, p[0]);
+		spa_json_builder_array_double(&b, p[1]);
+		spa_json_builder_array_double(&b, p[2]);
+		spa_json_builder_pop(&b, "]");
+
 		str += len;
 		if (*str != ',')
 			break;
 		str++;
 		i++;
 	}
-	fprintf(f, " ]");
-	fclose(f);
+	spa_json_builder_pop(&b, "]");
+	spa_json_builder_close(&b);
 
 	pw_properties_set(props, pw_key, args);
 	free(args);
diff --git a/src/modules/module-protocol-pulse/modules/module-jackdbus-detect.c b/src/modules/module-protocol-pulse/modules/module-jackdbus-detect.c
index c015673f9..cf07a7bcb 100644
--- a/src/modules/module-protocol-pulse/modules/module-jackdbus-detect.c
+++ b/src/modules/module-protocol-pulse/modules/module-jackdbus-detect.c
@@ -3,6 +3,7 @@
 /* SPDX-License-Identifier: MIT */
 
 #include <spa/utils/hook.h>
+#include <spa/utils/json-builder.h>
 #include <pipewire/pipewire.h>
 
 #include "../defs.h"
@@ -70,26 +71,29 @@ static const struct pw_impl_module_events module_events = {
 static int module_jackdbus_detect_load(struct module *module)
 {
 	struct module_jackdbus_detect_data *data = module->user_data;
-	FILE *f;
+	struct spa_json_builder b;
 	char *args;
 	size_t size;
+	int res;
 
 	pw_properties_setf(data->sink_props, "pulse.module.id",
 			"%u", module->index);
 	pw_properties_setf(data->source_props, "pulse.module.id",
 			"%u", module->index);
 
-	if ((f = open_memstream(&args, &size)) == NULL)
-		return -errno;
+	if ((res = spa_json_builder_memstream(&b, &args, &size, 0)) < 0)
+		return res;
 
-	fprintf(f, "{");
-	pw_properties_serialize_dict(f, &data->props->dict, 0);
-	fprintf(f, " source.props = {");
-	pw_properties_serialize_dict(f, &data->source_props->dict, 0);
-	fprintf(f, " } sink.props = {");
-	pw_properties_serialize_dict(f, &data->sink_props->dict, 0);
-	fprintf(f, " } }");
-	fclose(f);
+	spa_json_builder_array_push(&b, "{");
+	pw_properties_serialize_dict(b.f, &data->props->dict, 0);
+	spa_json_builder_object_push(&b, "source.props", "{");
+	pw_properties_serialize_dict(b.f, &data->source_props->dict, 0);
+	spa_json_builder_pop(&b, "}");
+	spa_json_builder_object_push(&b, "sink.props", "{");
+	pw_properties_serialize_dict(b.f, &data->sink_props->dict, 0);
+	spa_json_builder_pop(&b, "}");
+	spa_json_builder_pop(&b, "}");
+	spa_json_builder_close(&b);
 
 	data->mod = pw_context_load_module(module->impl->context,
 			"libpipewire-module-jackdbus-detect",
diff --git a/src/modules/module-protocol-pulse/modules/module-ladspa-sink.c b/src/modules/module-protocol-pulse/modules/module-ladspa-sink.c
index 4c9f33c47..049433add 100644
--- a/src/modules/module-protocol-pulse/modules/module-ladspa-sink.c
+++ b/src/modules/module-protocol-pulse/modules/module-ladspa-sink.c
@@ -3,7 +3,7 @@
 /* SPDX-License-Identifier: MIT */
 
 #include <spa/utils/hook.h>
-#include <spa/utils/json.h>
+#include <spa/utils/json-builder.h>
 #include <spa/param/audio/format-utils.h>
 
 #include <pipewire/pipewire.h>
@@ -73,11 +73,11 @@ static const struct pw_impl_module_events module_events = {
 static int module_ladspa_sink_load(struct module *module)
 {
 	struct module_ladspa_sink_data *data = module->user_data;
-	FILE *f;
+	struct spa_json_builder b;
 	char *args;
 	const char *str, *plugin, *label;
-	char encoded_plugin[1024], encoded_label[1024];
 	size_t size;
+	int res;
 
 	if ((plugin = pw_properties_get(module->props, "plugin")) == NULL)
 		return -EINVAL;
@@ -89,43 +89,59 @@ static int module_ladspa_sink_load(struct module *module)
 	pw_properties_setf(data->capture_props, "pulse.module.id", "%u", module->index);
 	pw_properties_setf(data->playback_props, "pulse.module.id", "%u", module->index);
 
-	if ((f = open_memstream(&args, &size)) == NULL)
-		return -errno;
+	if ((res = spa_json_builder_memstream(&b, &args, &size, 0)) < 0)
+		return res;
 
-	fprintf(f, "{");
-	pw_properties_serialize_dict(f, &module->props->dict, 0);
-	fprintf(f, " filter.graph = {");
-	fprintf(f, " nodes = [ { ");
-	spa_json_encode_string(encoded_plugin, sizeof(encoded_plugin), plugin);
-	spa_json_encode_string(encoded_label, sizeof(encoded_label), label);
-
-	fprintf(f, " type = ladspa ");
-	fprintf(f, " plugin = %s ", encoded_plugin);
-	fprintf(f, " label = %s ", encoded_label);
+	spa_json_builder_array_push(&b, "{");
+	pw_properties_serialize_dict(b.f, &module->props->dict, 0);
+	spa_json_builder_object_push(&b,  "filter.graph", "{");
+	spa_json_builder_object_push(&b,    "nodes", "[");
+	spa_json_builder_array_push(&b,       "{");
+	spa_json_builder_object_string(&b,      "type", "ladspa");
+	spa_json_builder_object_string(&b,      "plugin", plugin);
+	spa_json_builder_object_string(&b,      "label", label);
 	if ((str = pw_properties_get(module->props, "control")) != NULL) {
+		int count = 0;
 		size_t len;
 		const char *s, *state = NULL;
-		int count = 0;
 
-		fprintf(f, " control = {");
+		spa_json_builder_object_push(&b, "control", "{");
 		while ((s = pw_split_walk(str, ", ", &len, &state))) {
-			fprintf(f, " \"%d\" = %.*s", count, (int)len, s);
+			char key[16];
+			snprintf(key, sizeof(key), "%d", count);
+			spa_json_builder_object_value_full(&b, false,
+					key, INT_MAX, s, len);
 			count++;
 		}
-		fprintf(f, " }");
+		spa_json_builder_pop(&b,         "}");
 	}
-	fprintf(f, " } ]");
-	if ((str = pw_properties_get(module->props, "inputs")) != NULL)
-		fprintf(f, " inputs = [ %s ] ", str);
-	if ((str = pw_properties_get(module->props, "outputs")) != NULL)
-		fprintf(f, " outputs = [ %s ] ", str);
-	fprintf(f, " }");
-	fprintf(f, " capture.props = {");
-	pw_properties_serialize_dict(f, &data->capture_props->dict, 0);
-	fprintf(f, " } playback.props = {");
-	pw_properties_serialize_dict(f, &data->playback_props->dict, 0);
-	fprintf(f, " } }");
-	fclose(f);
+	spa_json_builder_pop(&b,              "}");
+	spa_json_builder_pop(&b,            "]");
+	if ((str = pw_properties_get(module->props, "input_ladspaport_map")) != NULL) {
+		const char *s, *state = NULL;
+		size_t len;
+		spa_json_builder_object_push(&b, "inputs", "[");
+		while ((s = pw_split_walk(str, ", ", &len, &state)))
+			spa_json_builder_add_simple(&b, NULL, 0, 'S', s, len);
+		spa_json_builder_pop(&b,         "]");
+	}
+	if ((str = pw_properties_get(module->props, "output_ladspaport_map")) != NULL) {
+		const char *s, *state = NULL;
+		size_t len;
+		spa_json_builder_object_push(&b, "outputs", "[");
+		while ((s = pw_split_walk(str, ", ", &len, &state)))
+			spa_json_builder_add_simple(&b, NULL, 0, 'S', s, len);
+		spa_json_builder_pop(&b,         "]");
+	}
+	spa_json_builder_pop(&b,          "}");
+	spa_json_builder_object_push(&b,  "capture.props", "{");
+	pw_properties_serialize_dict(b.f, &data->capture_props->dict, 0);
+	spa_json_builder_pop(&b,          "}");
+	spa_json_builder_object_push(&b,  "playback.props", "{");
+	pw_properties_serialize_dict(b.f, &data->playback_props->dict, 0);
+	spa_json_builder_pop(&b,          "}");
+	spa_json_builder_pop(&b,        "}");
+	spa_json_builder_close(&b);
 
 	data->mod = pw_context_load_module(module->impl->context,
 			"libpipewire-module-filter-chain",
diff --git a/src/modules/module-protocol-pulse/modules/module-ladspa-source.c b/src/modules/module-protocol-pulse/modules/module-ladspa-source.c
index d4883b551..94b3c428c 100644
--- a/src/modules/module-protocol-pulse/modules/module-ladspa-source.c
+++ b/src/modules/module-protocol-pulse/modules/module-ladspa-source.c
@@ -3,7 +3,7 @@
 /* SPDX-License-Identifier: MIT */
 
 #include <spa/utils/hook.h>
-#include <spa/utils/json.h>
+#include <spa/utils/json-builder.h>
 #include <spa/param/audio/format-utils.h>
 
 #include <pipewire/pipewire.h>
@@ -73,11 +73,11 @@ static const struct pw_impl_module_events module_events = {
 static int module_ladspa_source_load(struct module *module)
 {
 	struct module_ladspa_source_data *data = module->user_data;
-	FILE *f;
+	struct spa_json_builder b;
 	char *args;
 	const char *str, *plugin, *label;
-	char encoded_plugin[1024], encoded_label[1024];
 	size_t size;
+	int res;
 
 	if ((plugin = pw_properties_get(module->props, "plugin")) == NULL)
 		return -EINVAL;
@@ -89,43 +89,59 @@ static int module_ladspa_source_load(struct module *module)
 	pw_properties_setf(data->capture_props, "pulse.module.id", "%u", module->index);
 	pw_properties_setf(data->playback_props, "pulse.module.id", "%u", module->index);
 
-	if ((f = open_memstream(&args, &size)) == NULL)
-		return -errno;
+	if ((res = spa_json_builder_memstream(&b, &args, &size, 0)) < 0)
+		return res;
 
-	fprintf(f, "{");
-	pw_properties_serialize_dict(f, &module->props->dict, 0);
-	fprintf(f, " filter.graph = {");
-	fprintf(f, " nodes = [ { ");
-	spa_json_encode_string(encoded_plugin, sizeof(encoded_plugin), plugin);
-	spa_json_encode_string(encoded_label, sizeof(encoded_label), label);
-
-	fprintf(f, " type = ladspa ");
-	fprintf(f, " plugin = %s ", encoded_plugin);
-	fprintf(f, " label = %s ", encoded_label);
+	spa_json_builder_array_push(&b, "{");
+	pw_properties_serialize_dict(b.f, &module->props->dict, 0);
+	spa_json_builder_object_push(&b,  "filter.graph", "{");
+	spa_json_builder_object_push(&b,    "nodes", "[");
+	spa_json_builder_array_push(&b,       "{");
+	spa_json_builder_object_string(&b,      "type", "ladspa");
+	spa_json_builder_object_string(&b,      "plugin", plugin);
+	spa_json_builder_object_string(&b,      "label", label);
 	if ((str = pw_properties_get(module->props, "control")) != NULL) {
 		size_t len;
 		const char *s, *state = NULL;
 		int count = 0;
 
-		fprintf(f, " control = {");
+		spa_json_builder_object_push(&b, "control", "{");
 		while ((s = pw_split_walk(str, ", ", &len, &state))) {
-			fprintf(f, " \"%d\" = %.*s", count, (int)len, s);
+			char key[16];
+			snprintf(key, sizeof(key), "%d", count);
+			spa_json_builder_object_value_full(&b, false,
+					key, INT_MAX, s, len);
 			count++;
 		}
-		fprintf(f, " }");
+		spa_json_builder_pop(&b,         "}");
 	}
-	fprintf(f, " } ]");
-	if ((str = pw_properties_get(module->props, "inputs")) != NULL)
-		fprintf(f, " inputs = [ %s ] ", str);
-	if ((str = pw_properties_get(module->props, "outputs")) != NULL)
-		fprintf(f, " outputs = [ %s ] ", str);
-	fprintf(f, " }");
-	fprintf(f, " capture.props = {");
-	pw_properties_serialize_dict(f, &data->capture_props->dict, 0);
-	fprintf(f, " } playback.props = {");
-	pw_properties_serialize_dict(f, &data->playback_props->dict, 0);
-	fprintf(f, " } }");
-	fclose(f);
+	spa_json_builder_pop(&b,              "}");
+	spa_json_builder_pop(&b,            "]");
+	if ((str = pw_properties_get(module->props, "input_ladspaport_map")) != NULL) {
+		const char *s, *state = NULL;
+		size_t len;
+		spa_json_builder_object_push(&b, "inputs", "[");
+		while ((s = pw_split_walk(str, ", ", &len, &state)))
+			spa_json_builder_add_simple(&b, NULL, 0, 'S', s, len);
+		spa_json_builder_pop(&b,         "]");
+	}
+	if ((str = pw_properties_get(module->props, "output_ladspaport_map")) != NULL) {
+		const char *s, *state = NULL;
+		size_t len;
+		spa_json_builder_object_push(&b, "outputs", "[");
+		while ((s = pw_split_walk(str, ", ", &len, &state)))
+			spa_json_builder_add_simple(&b, NULL, 0, 'S', s, len);
+		spa_json_builder_pop(&b,         "]");
+	}
+	spa_json_builder_pop(&b,          "}");
+	spa_json_builder_object_push(&b,  "capture.props", "{");
+	pw_properties_serialize_dict(b.f, &data->capture_props->dict, 0);
+	spa_json_builder_pop(&b,          "}");
+	spa_json_builder_object_push(&b,  "playback.props", "{");
+	pw_properties_serialize_dict(b.f, &data->playback_props->dict, 0);
+	spa_json_builder_pop(&b,          "}");
+	spa_json_builder_pop(&b,        "}");
+	spa_json_builder_close(&b);
 
 	data->mod = pw_context_load_module(module->impl->context,
 			"libpipewire-module-filter-chain",
diff --git a/src/modules/module-protocol-pulse/modules/module-loopback.c b/src/modules/module-protocol-pulse/modules/module-loopback.c
index 2ef85fa5e..5808e196e 100644
--- a/src/modules/module-protocol-pulse/modules/module-loopback.c
+++ b/src/modules/module-protocol-pulse/modules/module-loopback.c
@@ -5,7 +5,7 @@
 
 #include <spa/param/audio/format-utils.h>
 #include <spa/utils/hook.h>
-#include <spa/utils/json.h>
+#include <spa/utils/json-builder.h>
 #include <pipewire/pipewire.h>
 
 #include "../defs.h"
@@ -71,26 +71,29 @@ static const struct pw_impl_module_events module_events = {
 static int module_loopback_load(struct module *module)
 {
 	struct module_loopback_data *data = module->user_data;
-	FILE *f;
+	struct spa_json_builder b;
 	char *args;
 	size_t size;
+	int res;
 
 	pw_properties_setf(data->capture_props, PW_KEY_NODE_GROUP, "loopback-%u", module->index);
 	pw_properties_setf(data->playback_props, PW_KEY_NODE_GROUP, "loopback-%u", module->index);
 	pw_properties_setf(data->capture_props, "pulse.module.id", "%u", module->index);
 	pw_properties_setf(data->playback_props, "pulse.module.id", "%u", module->index);
 
-	if ((f = open_memstream(&args, &size)) == NULL)
-		return -errno;
+	if ((res = spa_json_builder_memstream(&b, &args, &size, 0)) < 0)
+		return res;
 
-	fprintf(f, "{");
-	pw_properties_serialize_dict(f, &data->global_props->dict, 0);
-	fprintf(f, " capture.props = {");
-	pw_properties_serialize_dict(f, &data->capture_props->dict, 0);
-	fprintf(f, " } playback.props = {");
-	pw_properties_serialize_dict(f, &data->playback_props->dict, 0);
-	fprintf(f, " } }");
-	fclose(f);
+	spa_json_builder_array_push(&b, "{");
+	pw_properties_serialize_dict(b.f, &data->global_props->dict, 0);
+	spa_json_builder_object_push(&b,  "capture.props", "{");
+	pw_properties_serialize_dict(b.f, &data->capture_props->dict, 0);
+	spa_json_builder_pop(&b,          "}");
+	spa_json_builder_object_push(&b,  "playback.props", "{");
+	pw_properties_serialize_dict(b.f, &data->playback_props->dict, 0);
+	spa_json_builder_pop(&b,          "}");
+	spa_json_builder_pop(&b,        "}");
+	spa_json_builder_close(&b);
 
 	data->mod = pw_context_load_module(module->impl->context,
 			"libpipewire-module-loopback",
diff --git a/src/modules/module-protocol-pulse/modules/module-native-protocol-tcp.c b/src/modules/module-protocol-pulse/modules/module-native-protocol-tcp.c
index 1d0fbb5ab..071322658 100644
--- a/src/modules/module-protocol-pulse/modules/module-native-protocol-tcp.c
+++ b/src/modules/module-protocol-pulse/modules/module-native-protocol-tcp.c
@@ -2,7 +2,7 @@
 /* SPDX-FileCopyrightText: Copyright © 2021 Wim Taymans <wim.taymans@gmail.com> */
 /* SPDX-License-Identifier: MIT */
 
-#include <spa/utils/json.h>
+#include <spa/utils/json-builder.h>
 #include <pipewire/pipewire.h>
 
 #include "../module.h"
@@ -79,10 +79,10 @@ static int module_native_protocol_tcp_prepare(struct module * const module)
 	struct module_native_protocol_tcp_data * const d = module->user_data;
 	struct pw_properties * const props = module->props;
 	const char *port, *listen, *auth;
-	char address[1024], encoded[1024];
-	FILE *f;
+	struct spa_json_builder b;
 	char *args;
 	size_t size;
+	int res;
 
 	PW_LOG_TOPIC_INIT(mod_topic);
 
@@ -93,20 +93,18 @@ static int module_native_protocol_tcp_prepare(struct module * const module)
 
 	auth = pw_properties_get(props, "auth-anonymous");
 
-	f = open_memstream(&args, &size);
-	if (f == NULL)
-		return -errno;
+	if ((res = spa_json_builder_memstream(&b, &args, &size, 0)) < 0)
+		return res;
 
-	snprintf(address, sizeof(address), "tcp:%s%s%s",
+	spa_json_builder_array_push(&b, "[");
+	spa_json_builder_array_push(&b,   "{");
+	spa_json_builder_object_stringf(&b,  "address", "tcp:%s%s%s",
 			listen ? listen : "", listen ? ":" : "", port);
-	spa_json_encode_string(encoded, sizeof(encoded), address);
-
-	fprintf(f, "[ { ");
-	fprintf(f, " \"address\": %s ", encoded);
 	if (auth && module_args_parse_bool(auth))
-		fprintf(f, " \"client.access\": \"unrestricted\" ");
-	fprintf(f, "} ]");
-	fclose(f);
+		spa_json_builder_object_string(&b, "client.access", "unrestricted");
+	spa_json_builder_pop(&b,          "}");
+	spa_json_builder_pop(&b,        "]");
+	spa_json_builder_close(&b);
 
 	pw_properties_set(props, "pulse.tcp", args);
 	free(args);
diff --git a/src/modules/module-protocol-pulse/modules/module-pipe-sink.c b/src/modules/module-protocol-pulse/modules/module-pipe-sink.c
index 0f910ac6b..c80caecc0 100644
--- a/src/modules/module-protocol-pulse/modules/module-pipe-sink.c
+++ b/src/modules/module-protocol-pulse/modules/module-pipe-sink.c
@@ -7,6 +7,7 @@
 #include <sys/stat.h>
 #include <unistd.h>
 
+#include <spa/utils/json-builder.h>
 #include <pipewire/pipewire.h>
 #include <spa/param/audio/format-utils.h>
 #include <spa/utils/hook.h>
@@ -70,22 +71,24 @@ static const struct pw_impl_module_events module_events = {
 static int module_pipe_sink_load(struct module *module)
 {
 	struct module_pipesink_data *data = module->user_data;
-	FILE *f;
+	struct spa_json_builder b;
 	char *args;
 	size_t size;
+	int res;
 
 	pw_properties_setf(data->stream_props, "pulse.module.id",
 			"%u", module->index);
 
-	if ((f = open_memstream(&args, &size)) == NULL)
-		return -errno;
+	if ((res = spa_json_builder_memstream(&b, &args, &size, 0)) < 0)
+		return res;
 
-	fprintf(f, "{");
-	pw_properties_serialize_dict(f, &data->global_props->dict, 0);
-	fprintf(f, " \"stream.props\": {");
-	pw_properties_serialize_dict(f, &data->stream_props->dict, 0);
-	fprintf(f, " } }");
-	fclose(f);
+	spa_json_builder_array_push(&b, "{");
+	pw_properties_serialize_dict(b.f, &data->global_props->dict, 0);
+	spa_json_builder_object_push(&b,  "stream.props", "{");
+	pw_properties_serialize_dict(b.f, &data->stream_props->dict, 0);
+	spa_json_builder_pop(&b,          "}");
+	spa_json_builder_pop(&b,        "}");
+	spa_json_builder_close(&b);
 
 	data->mod = pw_context_load_module(module->impl->context,
 			"libpipewire-module-pipe-tunnel",
diff --git a/src/modules/module-protocol-pulse/modules/module-pipe-source.c b/src/modules/module-protocol-pulse/modules/module-pipe-source.c
index ff44f3c38..4e69d1d6b 100644
--- a/src/modules/module-protocol-pulse/modules/module-pipe-source.c
+++ b/src/modules/module-protocol-pulse/modules/module-pipe-source.c
@@ -7,6 +7,7 @@
 #include <sys/stat.h>
 #include <unistd.h>
 
+#include <spa/utils/json-builder.h>
 #include <pipewire/pipewire.h>
 #include <spa/param/audio/format-utils.h>
 #include <spa/utils/hook.h>
@@ -69,22 +70,24 @@ static const struct pw_impl_module_events module_events = {
 static int module_pipe_source_load(struct module *module)
 {
 	struct module_pipesrc_data *data = module->user_data;
-	FILE *f;
+	struct spa_json_builder b;
 	char *args;
 	size_t size;
+	int res;
 
 	pw_properties_setf(data->stream_props, "pulse.module.id",
 			"%u", module->index);
 
-	if ((f = open_memstream(&args, &size)) == NULL)
-		return -errno;
+	if ((res = spa_json_builder_memstream(&b, &args, &size, 0)) < 0)
+		return res;
 
-	fprintf(f, "{");
-	pw_properties_serialize_dict(f, &data->global_props->dict, 0);
-	fprintf(f, " \"stream.props\": {");
-	pw_properties_serialize_dict(f, &data->stream_props->dict, 0);
-	fprintf(f, " } }");
-	fclose(f);
+	spa_json_builder_array_push(&b, "{");
+	pw_properties_serialize_dict(b.f, &data->global_props->dict, 0);
+	spa_json_builder_object_push(&b,  "stream.props", "{");
+	pw_properties_serialize_dict(b.f, &data->stream_props->dict, 0);
+	spa_json_builder_pop(&b,          "}");
+	spa_json_builder_pop(&b,        "}");
+	spa_json_builder_close(&b);
 
 	data->mod = pw_context_load_module(module->impl->context,
 			"libpipewire-module-pipe-tunnel",
diff --git a/src/modules/module-protocol-pulse/modules/module-raop-discover.c b/src/modules/module-protocol-pulse/modules/module-raop-discover.c
index 4e1cf8adb..d1c06e183 100644
--- a/src/modules/module-protocol-pulse/modules/module-raop-discover.c
+++ b/src/modules/module-protocol-pulse/modules/module-raop-discover.c
@@ -3,6 +3,7 @@
 /* SPDX-License-Identifier: MIT */
 
 #include <spa/utils/hook.h>
+#include <spa/utils/json-builder.h>
 #include <pipewire/pipewire.h>
 
 #include "../defs.h"
@@ -54,18 +55,19 @@ static const struct pw_impl_module_events module_events = {
 static int module_raop_discover_load(struct module *module)
 {
 	struct module_raop_discover_data *data = module->user_data;
-	FILE *f;
+	struct spa_json_builder b;
 	char *args;
 	size_t size;
+	int res;
 
-	if ((f = open_memstream(&args, &size)) == NULL)
-		return -errno;
+	if ((res = spa_json_builder_memstream(&b, &args, &size, 0)) < 0)
+		return res;
 
-	fprintf(f, "{");
+	spa_json_builder_array_push(&b, "{");
 	if (data->latency_msec > 0)
-		fprintf(f, " raop.latency.ms = %u ", data->latency_msec);
-	fprintf(f, "}");
-	fclose(f);
+		spa_json_builder_object_uint(&b, "raop.latency.ms", data->latency_msec);
+	spa_json_builder_pop(&b,        "}");
+	spa_json_builder_close(&b);
 
 	data->mod = pw_context_load_module(module->impl->context,
 			"libpipewire-module-raop-discover",
diff --git a/src/modules/module-protocol-pulse/modules/module-remap-sink.c b/src/modules/module-protocol-pulse/modules/module-remap-sink.c
index 103579fe2..92feb5543 100644
--- a/src/modules/module-protocol-pulse/modules/module-remap-sink.c
+++ b/src/modules/module-protocol-pulse/modules/module-remap-sink.c
@@ -4,7 +4,7 @@
 
 #include <spa/param/audio/format-utils.h>
 #include <spa/utils/hook.h>
-#include <spa/utils/json.h>
+#include <spa/utils/json-builder.h>
 #include <pipewire/pipewire.h>
 
 #include "../defs.h"
@@ -68,26 +68,29 @@ static const struct pw_impl_module_events module_events = {
 static int module_remap_sink_load(struct module *module)
 {
 	struct module_remap_sink_data *data = module->user_data;
-	FILE *f;
+	struct spa_json_builder b;
 	char *args;
 	size_t size;
+	int res;
 
 	pw_properties_setf(data->capture_props, PW_KEY_NODE_GROUP, "remap-sink-%u", module->index);
 	pw_properties_setf(data->playback_props, PW_KEY_NODE_GROUP, "remap-sink-%u", module->index);
 	pw_properties_setf(data->capture_props, "pulse.module.id", "%u", module->index);
 	pw_properties_setf(data->playback_props, "pulse.module.id", "%u", module->index);
 
-	if ((f = open_memstream(&args, &size)) == NULL)
-		return -errno;
+	if ((res = spa_json_builder_memstream(&b, &args, &size, 0)) < 0)
+		return res;
 
-	fprintf(f, "{");
-	pw_properties_serialize_dict(f, &module->props->dict, 0);
-	fprintf(f, " capture.props = {");
-	pw_properties_serialize_dict(f, &data->capture_props->dict, 0);
-	fprintf(f, " } playback.props = {");
-	pw_properties_serialize_dict(f, &data->playback_props->dict, 0);
-	fprintf(f, " } }");
-	fclose(f);
+	spa_json_builder_array_push(&b, "{");
+	pw_properties_serialize_dict(b.f, &module->props->dict, 0);
+	spa_json_builder_object_push(&b,  "capture.props", "{");
+	pw_properties_serialize_dict(b.f, &data->capture_props->dict, 0);
+	spa_json_builder_pop(&b,          "}");
+	spa_json_builder_object_push(&b,  "playback.props", "{");
+	pw_properties_serialize_dict(b.f, &data->playback_props->dict, 0);
+	spa_json_builder_pop(&b,          "}");
+	spa_json_builder_pop(&b,        "}");
+	spa_json_builder_close(&b);
 
 	data->mod = pw_context_load_module(module->impl->context,
 			"libpipewire-module-loopback",
diff --git a/src/modules/module-protocol-pulse/modules/module-remap-source.c b/src/modules/module-protocol-pulse/modules/module-remap-source.c
index eaff91b08..d67f150df 100644
--- a/src/modules/module-protocol-pulse/modules/module-remap-source.c
+++ b/src/modules/module-protocol-pulse/modules/module-remap-source.c
@@ -4,7 +4,7 @@
 
 #include <spa/param/audio/format-utils.h>
 #include <spa/utils/hook.h>
-#include <spa/utils/json.h>
+#include <spa/utils/json-builder.h>
 #include <pipewire/pipewire.h>
 
 #include "../defs.h"
@@ -68,26 +68,29 @@ static const struct pw_impl_module_events module_events = {
 static int module_remap_source_load(struct module *module)
 {
 	struct module_remap_source_data *data = module->user_data;
-	FILE *f;
+	struct spa_json_builder b;
 	char *args;
 	size_t size;
+	int res;
 
 	pw_properties_setf(data->capture_props, PW_KEY_NODE_GROUP, "remap-source-%u", module->index);
 	pw_properties_setf(data->playback_props, PW_KEY_NODE_GROUP, "remap-source-%u", module->index);
 	pw_properties_setf(data->capture_props, "pulse.module.id", "%u", module->index);
 	pw_properties_setf(data->playback_props, "pulse.module.id", "%u", module->index);
 
-	if ((f = open_memstream(&args, &size)) == NULL)
-		return -errno;
+	if ((res = spa_json_builder_memstream(&b, &args, &size, 0)) < 0)
+		return res;
 
-	fprintf(f, "{");
-	pw_properties_serialize_dict(f, &module->props->dict, 0);
-	fprintf(f, " capture.props = { ");
-	pw_properties_serialize_dict(f, &data->capture_props->dict, 0);
-	fprintf(f, " } playback.props = { ");
-	pw_properties_serialize_dict(f, &data->playback_props->dict, 0);
-	fprintf(f, " } }");
-	fclose(f);
+	spa_json_builder_array_push(&b, "{");
+	pw_properties_serialize_dict(b.f, &module->props->dict, 0);
+	spa_json_builder_object_push(&b,  "capture.props", "{");
+	pw_properties_serialize_dict(b.f, &data->capture_props->dict, 0);
+	spa_json_builder_pop(&b,          "}");
+	spa_json_builder_object_push(&b,  "playback.props", "{");
+	pw_properties_serialize_dict(b.f, &data->playback_props->dict, 0);
+	spa_json_builder_pop(&b,          "}");
+	spa_json_builder_pop(&b,        "}");
+	spa_json_builder_close(&b);
 
 	data->mod = pw_context_load_module(module->impl->context,
 			"libpipewire-module-loopback",
diff --git a/src/modules/module-protocol-pulse/modules/module-roc-sink-input.c b/src/modules/module-protocol-pulse/modules/module-roc-sink-input.c
index 2200a7bfc..76e6eebba 100644
--- a/src/modules/module-protocol-pulse/modules/module-roc-sink-input.c
+++ b/src/modules/module-protocol-pulse/modules/module-roc-sink-input.c
@@ -4,6 +4,7 @@
 /* SPDX-License-Identifier: MIT */
 
 #include <spa/utils/hook.h>
+#include <spa/utils/json-builder.h>
 #include <pipewire/pipewire.h>
 
 #include "../defs.h"
@@ -67,22 +68,24 @@ static const struct pw_impl_module_events module_events = {
 static int module_roc_sink_input_load(struct module *module)
 {
 	struct module_roc_sink_input_data *data = module->user_data;
-	FILE *f;
+	struct spa_json_builder b;
 	char *args;
 	size_t size;
+	int res;
 
 	pw_properties_setf(data->source_props, "pulse.module.id",
 			"%u", module->index);
 
-	if ((f = open_memstream(&args, &size)) == NULL)
-		return -errno;
+	if ((res = spa_json_builder_memstream(&b, &args, &size, 0)) < 0)
+		return res;
 
-	fprintf(f, "{");
-	pw_properties_serialize_dict(f, &data->roc_props->dict, 0);
-	fprintf(f, " source.props = {");
-	pw_properties_serialize_dict(f, &data->source_props->dict, 0);
-	fprintf(f, " } }");
-	fclose(f);
+	spa_json_builder_array_push(&b, "{");
+	pw_properties_serialize_dict(b.f, &data->roc_props->dict, 0);
+	spa_json_builder_object_push(&b,  "source.props", "{");
+	pw_properties_serialize_dict(b.f, &data->source_props->dict, 0);
+	spa_json_builder_pop(&b,          "}");
+	spa_json_builder_pop(&b,        "}");
+	spa_json_builder_close(&b);
 
 	data->mod = pw_context_load_module(module->impl->context,
 			"libpipewire-module-roc-source",
diff --git a/src/modules/module-protocol-pulse/modules/module-roc-sink.c b/src/modules/module-protocol-pulse/modules/module-roc-sink.c
index 6b03006ab..bdddadda2 100644
--- a/src/modules/module-protocol-pulse/modules/module-roc-sink.c
+++ b/src/modules/module-protocol-pulse/modules/module-roc-sink.c
@@ -4,6 +4,7 @@
 /* SPDX-License-Identifier: MIT */
 
 #include <spa/utils/hook.h>
+#include <spa/utils/json-builder.h>
 #include <pipewire/pipewire.h>
 
 #include "../defs.h"
@@ -65,22 +66,24 @@ static const struct pw_impl_module_events module_events = {
 static int module_roc_sink_load(struct module *module)
 {
 	struct module_roc_sink_data *data = module->user_data;
-	FILE *f;
+	struct spa_json_builder b;
 	char *args;
 	size_t size;
+	int res;
 
 	pw_properties_setf(data->sink_props, "pulse.module.id",
 			"%u", module->index);
 
-	if ((f = open_memstream(&args, &size)) == NULL)
-		return -errno;
+	if ((res = spa_json_builder_memstream(&b, &args, &size, 0)) < 0)
+		return res;
 
-	fprintf(f, "{");
-	pw_properties_serialize_dict(f, &data->roc_props->dict, 0);
-	fprintf(f, " sink.props = {");
-	pw_properties_serialize_dict(f, &data->sink_props->dict, 0);
-	fprintf(f, " } }");
-	fclose(f);
+	spa_json_builder_array_push(&b, "{");
+	pw_properties_serialize_dict(b.f, &data->roc_props->dict, 0);
+	spa_json_builder_object_push(&b,  "sink.props", "{");
+	pw_properties_serialize_dict(b.f, &data->sink_props->dict, 0);
+	spa_json_builder_pop(&b,          "}");
+	spa_json_builder_pop(&b,        "}");
+	spa_json_builder_close(&b);
 
 	data->mod = pw_context_load_module(module->impl->context,
 			"libpipewire-module-roc-sink",
diff --git a/src/modules/module-protocol-pulse/modules/module-roc-source.c b/src/modules/module-protocol-pulse/modules/module-roc-source.c
index 661153d1e..4607ffbd6 100644
--- a/src/modules/module-protocol-pulse/modules/module-roc-source.c
+++ b/src/modules/module-protocol-pulse/modules/module-roc-source.c
@@ -4,6 +4,7 @@
 /* SPDX-License-Identifier: MIT */
 
 #include <spa/utils/hook.h>
+#include <spa/utils/json-builder.h>
 #include <pipewire/pipewire.h>
 
 #include "../defs.h"
@@ -67,22 +68,24 @@ static const struct pw_impl_module_events module_events = {
 static int module_roc_source_load(struct module *module)
 {
 	struct module_roc_source_data *data = module->user_data;
-	FILE *f;
+	struct spa_json_builder b;
 	char *args;
 	size_t size;
+	int res;
 
 	pw_properties_setf(data->source_props, "pulse.module.id",
 			"%u", module->index);
 
-	if ((f = open_memstream(&args, &size)) == NULL)
-		return -errno;
+	if ((res = spa_json_builder_memstream(&b, &args, &size, 0)) < 0)
+		return res;
 
-	fprintf(f, "{");
-	pw_properties_serialize_dict(f, &data->roc_props->dict, 0);
-	fprintf(f, " source.props = {");
-	pw_properties_serialize_dict(f, &data->source_props->dict, 0);
-	fprintf(f, " } }");
-	fclose(f);
+	spa_json_builder_array_push(&b, "{");
+	pw_properties_serialize_dict(b.f, &data->roc_props->dict, 0);
+	spa_json_builder_object_push(&b,  "source.props", "{");
+	pw_properties_serialize_dict(b.f, &data->source_props->dict, 0);
+	spa_json_builder_pop(&b,          "}");
+	spa_json_builder_pop(&b,        "}");
+	spa_json_builder_close(&b);
 
 	data->mod = pw_context_load_module(module->impl->context,
 			"libpipewire-module-roc-source",
diff --git a/src/modules/module-protocol-pulse/modules/module-rtp-recv.c b/src/modules/module-protocol-pulse/modules/module-rtp-recv.c
index f81e19047..fc6e2491c 100644
--- a/src/modules/module-protocol-pulse/modules/module-rtp-recv.c
+++ b/src/modules/module-protocol-pulse/modules/module-rtp-recv.c
@@ -3,6 +3,7 @@
 /* SPDX-License-Identifier: MIT */
 
 #include <spa/utils/hook.h>
+#include <spa/utils/json-builder.h>
 #include <pipewire/pipewire.h>
 
 #include "../defs.h"
@@ -60,25 +61,35 @@ static const struct pw_impl_module_events module_events = {
 static int module_rtp_recv_load(struct module *module)
 {
 	struct module_rtp_recv_data *data = module->user_data;
-	FILE *f;
+	struct spa_json_builder b;
 	char *args;
 	size_t size;
+	int res;
 
 	pw_properties_setf(data->stream_props, "pulse.module.id",
 			"%u", module->index);
 
-	if ((f = open_memstream(&args, &size)) == NULL)
-		return -errno;
+	if ((res = spa_json_builder_memstream(&b, &args, &size, 0)) < 0)
+		return res;
 
-	fprintf(f, "{");
-	pw_properties_serialize_dict(f, &data->global_props->dict, 0);
-	fprintf(f, " stream.rules = ");
-	fprintf(f, "[ { matches = [ { rtp.session = \"~.*\" } ] "),
-	fprintf(f, "    actions = { create-stream = { ");
-	pw_properties_serialize_dict(f, &data->stream_props->dict, 0);
-	fprintf(f, "    } } } ] ");
-	fprintf(f, " }");
-	fclose(f);
+	spa_json_builder_array_push(&b, "{");
+	pw_properties_serialize_dict(b.f, &data->global_props->dict, 0);
+	spa_json_builder_object_push(&b,  "stream.rules", "[");
+	spa_json_builder_array_push(&b,     "{");
+	spa_json_builder_object_push(&b,      "matches", "[");
+	spa_json_builder_array_push(&b,         "{");
+	spa_json_builder_object_string(&b,        "rtp.session", "~.*");
+	spa_json_builder_pop(&b,                "}");
+	spa_json_builder_pop(&b,              "]");
+	spa_json_builder_object_push(&b,      "actions", "{");
+	spa_json_builder_object_push(&b,        "create-stream", "{");
+	pw_properties_serialize_dict(b.f, &data->stream_props->dict, 0);
+	spa_json_builder_pop(&b,                "}");
+	spa_json_builder_pop(&b,              "}");
+	spa_json_builder_pop(&b,            "}");
+	spa_json_builder_pop(&b,          "]");
+	spa_json_builder_pop(&b,        "}");
+	spa_json_builder_close(&b);
 
 	data->mod = pw_context_load_module(module->impl->context,
 			"libpipewire-module-rtp-sap",
diff --git a/src/modules/module-protocol-pulse/modules/module-rtp-send.c b/src/modules/module-protocol-pulse/modules/module-rtp-send.c
index aa4015d12..3a6d1d6c6 100644
--- a/src/modules/module-protocol-pulse/modules/module-rtp-send.c
+++ b/src/modules/module-protocol-pulse/modules/module-rtp-send.c
@@ -3,6 +3,7 @@
 /* SPDX-License-Identifier: MIT */
 
 #include <spa/utils/hook.h>
+#include <spa/utils/json-builder.h>
 #include <pipewire/pipewire.h>
 
 #include "../defs.h"
@@ -87,22 +88,24 @@ static const struct pw_impl_module_events sap_module_events = {
 static int module_rtp_send_load(struct module *module)
 {
 	struct module_rtp_send_data *data = module->user_data;
-	FILE *f;
+	struct spa_json_builder b;
 	char *args;
 	size_t size;
+	int res;
 
 	pw_properties_setf(data->stream_props, "pulse.module.id",
 			"%u", module->index);
 
-	if ((f = open_memstream(&args, &size)) == NULL)
-		return -errno;
+	if ((res = spa_json_builder_memstream(&b, &args, &size, 0)) < 0)
+		return res;
 
-	fprintf(f, "{");
-	pw_properties_serialize_dict(f, &data->global_props->dict, 0);
-	fprintf(f, " stream.props = {");
-	pw_properties_serialize_dict(f, &data->stream_props->dict, 0);
-	fprintf(f, " } }");
-	fclose(f);
+	spa_json_builder_array_push(&b, "{");
+	pw_properties_serialize_dict(b.f, &data->global_props->dict, 0);
+	spa_json_builder_object_push(&b,  "stream.props", "{");
+	pw_properties_serialize_dict(b.f, &data->stream_props->dict, 0);
+	spa_json_builder_pop(&b,          "}");
+	spa_json_builder_pop(&b,        "}");
+	spa_json_builder_close(&b);
 
 	data->mod = pw_context_load_module(module->impl->context,
 			"libpipewire-module-rtp-sink",
@@ -116,16 +119,26 @@ static int module_rtp_send_load(struct module *module)
 			&data->mod_listener,
 			&module_events, data);
 
-	if ((f = open_memstream(&args, &size)) == NULL)
-		return -errno;
+	if ((res = spa_json_builder_memstream(&b, &args, &size, 0)) < 0)
+		return res;
 
-	fprintf(f, "{");
-	pw_properties_serialize_dict(f, &data->sap_props->dict, 0);
-	fprintf(f, " stream.rules = [");
-	fprintf(f, "   { matches = [ { pulse.module.id = %u } ] ", module->index);
-	fprintf(f, "     actions = { announce-stream = { } } ");
-	fprintf(f, "   } ] }");
-	fclose(f);
+	spa_json_builder_array_push(&b, "{");
+	pw_properties_serialize_dict(b.f, &data->sap_props->dict, 0);
+	spa_json_builder_object_push(&b,  "stream.rules", "[");
+	spa_json_builder_array_push(&b,     "{");
+	spa_json_builder_object_push(&b,      "matches", "[");
+	spa_json_builder_array_push(&b,         "{");
+	spa_json_builder_object_uint(&b,          "pulse.module.id", module->index);
+	spa_json_builder_pop(&b,                "}");
+	spa_json_builder_pop(&b,              "]");
+	spa_json_builder_object_push(&b,      "actions", "{");
+	spa_json_builder_object_push(&b,        "announce-stream", "{");
+	spa_json_builder_pop(&b,                "}");
+	spa_json_builder_pop(&b,              "}");
+	spa_json_builder_pop(&b,            "}");
+	spa_json_builder_pop(&b,          "]");
+	spa_json_builder_pop(&b,        "}");
+	spa_json_builder_close(&b);
 
 	data->sap = pw_context_load_module(module->impl->context,
 			"libpipewire-module-rtp-sap",
diff --git a/src/modules/module-protocol-pulse/modules/module-simple-protocol-tcp.c b/src/modules/module-protocol-pulse/modules/module-simple-protocol-tcp.c
index 852cd87ab..edc52af07 100644
--- a/src/modules/module-protocol-pulse/modules/module-simple-protocol-tcp.c
+++ b/src/modules/module-protocol-pulse/modules/module-simple-protocol-tcp.c
@@ -2,7 +2,7 @@
 /* SPDX-FileCopyrightText: Copyright © 2021 Wim Taymans <wim.taymans@gmail.com> */
 /* SPDX-License-Identifier: MIT */
 
-#include <spa/utils/json.h>
+#include <spa/utils/json-builder.h>
 #include <pipewire/impl.h>
 #include <pipewire/pipewire.h>
 
@@ -70,17 +70,18 @@ static int module_simple_protocol_tcp_load(struct module *module)
 {
 	struct module_simple_protocol_tcp_data *data = module->user_data;
 	struct impl *impl = module->impl;
+	struct spa_json_builder b;
 	char *args;
 	size_t size;
-	FILE *f;
+	int res;
 
-	if ((f = open_memstream(&args, &size)) == NULL)
-		return -errno;
+	if ((res = spa_json_builder_memstream(&b, &args, &size, 0)) < 0)
+		return res;
 
-	fprintf(f, "{");
-	pw_properties_serialize_dict(f, &data->module_props->dict, 0);
-	fprintf(f, "}");
-	fclose(f);
+	spa_json_builder_array_push(&b, "{");
+	pw_properties_serialize_dict(b.f, &data->module_props->dict, 0);
+	spa_json_builder_pop(&b,        "}");
+	spa_json_builder_close(&b);
 
 	data->mod = pw_context_load_module(impl->context,
 			"libpipewire-module-protocol-simple",
@@ -171,11 +172,21 @@ static int module_simple_protocol_tcp_prepare(struct module * const module)
 	listen = pw_properties_get(props, "listen");
 
 	{
-		char address[1024], encoded[1024];
-		snprintf(address, sizeof(address), "tcp:%s%s%s",
+		struct spa_json_builder ab;
+		char *addr;
+		size_t addr_size;
+
+		if ((res = spa_json_builder_memstream(&ab, &addr, &addr_size, 0)) < 0)
+			goto out;
+
+		spa_json_builder_array_push(&ab, "[");
+		spa_json_builder_array_stringf(&ab, "tcp:%s%s%s",
 				listen ? listen : "", listen ? ":" : "", port);
-		spa_json_encode_string(encoded, sizeof(encoded), address);
-		pw_properties_setf(module_props, "server.address", "[ %s ]", encoded);
+		spa_json_builder_pop(&ab,        "]");
+		spa_json_builder_close(&ab);
+
+		pw_properties_set(module_props, "server.address", addr);
+		free(addr);
 	}
 
 	d->module = module;
diff --git a/src/modules/module-protocol-pulse/modules/module-stream-restore.c b/src/modules/module-protocol-pulse/modules/module-stream-restore.c
index 3304a0dec..a56a8e5f3 100644
--- a/src/modules/module-protocol-pulse/modules/module-stream-restore.c
+++ b/src/modules/module-protocol-pulse/modules/module-stream-restore.c
@@ -64,7 +64,7 @@ enum {
 #include <spa/utils/defs.h>
 #include <spa/utils/dict.h>
 #include <spa/utils/string.h>
-#include <spa/utils/json.h>
+#include <spa/utils/json-builder.h>
 #include <pipewire/log.h>
 #include <pipewire/properties.h>
 
@@ -262,10 +262,9 @@ static int do_extension_stream_restore_write(struct module *module, struct clien
 		struct volume vol;
 		bool mute = false;
 		uint32_t i;
-		FILE *f;
 		char *ptr;
 		size_t size;
-		char key[1024], buf[128];
+		char key[1024];
 
 		spa_zero(map);
 		spa_zero(vol);
@@ -282,35 +281,36 @@ static int do_extension_stream_restore_write(struct module *module, struct clien
 		if (name == NULL || name[0] == '\0')
 			return -EPROTO;
 
-		if ((f = open_memstream(&ptr, &size)) == NULL)
-			return -errno;
+		{
+		struct spa_json_builder b;
+		int bres;
 
-		fprintf(f, "{");
-		fprintf(f, " \"mute\": %s", mute ? "true" : "false");
+		if ((bres = spa_json_builder_memstream(&b, &ptr, &size, 0)) < 0)
+			return bres;
+
+		spa_json_builder_array_push(&b, "{");
+		spa_json_builder_object_bool(&b, "mute", mute);
 		if (vol.channels > 0) {
-			fprintf(f, ", \"volumes\": [");
+			spa_json_builder_object_push(&b, "volumes", "[");
 			for (i = 0; i < vol.channels; i++)
-				fprintf(f, "%s%s", (i == 0 ? " ":", "),
-						spa_json_format_float(buf, sizeof(buf), vol.values[i]));
-			fprintf(f, " ]");
+				spa_json_builder_array_double(&b, vol.values[i]);
+			spa_json_builder_pop(&b, "]");
 		}
 		if (map.channels > 0) {
 			char pos[8];
-			fprintf(f, ", \"channels\": [");
+			spa_json_builder_object_push(&b, "channels", "[");
 			for (i = 0; i < map.channels; i++)
-				fprintf(f, "%s\"%s\"", (i == 0 ? " ":", "),
+				spa_json_builder_array_string(&b,
 						channel_id2name(map.map[i], pos, sizeof(pos)));
-			fprintf(f, " ]");
+			spa_json_builder_pop(&b, "]");
 		}
 		if (device_name != NULL && device_name[0] &&
 		    (client->default_source == NULL || !spa_streq(device_name, client->default_source)) &&
-		    (client->default_sink == NULL || !spa_streq(device_name, client->default_sink))) {
-			char target[1024];
-			spa_json_encode_string(target, sizeof(target), device_name);
-			fprintf(f, ", \"target-node\": %s", target);
+		    (client->default_sink == NULL || !spa_streq(device_name, client->default_sink)))
+			spa_json_builder_object_string(&b, "target-node", device_name);
+		spa_json_builder_pop(&b, "}");
+		spa_json_builder_close(&b);
 		}
-		fprintf(f, " }");
-		fclose(f);
 		if (key_from_name(name, key, sizeof(key)) >= 0) {
 			pw_log_debug("%s -> %s: %s", name, key, ptr);
 			if ((res = pw_manager_set_metadata(client->manager,
diff --git a/src/modules/module-protocol-pulse/modules/module-switch-on-connect.c b/src/modules/module-protocol-pulse/modules/module-switch-on-connect.c
index 55c901d0b..33150d517 100644
--- a/src/modules/module-protocol-pulse/modules/module-switch-on-connect.c
+++ b/src/modules/module-protocol-pulse/modules/module-switch-on-connect.c
@@ -4,7 +4,7 @@
 /* SPDX-License-Identifier: MIT */
 
 #include <spa/utils/hook.h>
-#include <spa/utils/json.h>
+#include <spa/utils/json-builder.h>
 #include <spa/utils/string.h>
 
 #include <regex.h>
@@ -136,13 +136,23 @@ static void manager_added(void *data, struct pw_manager_object *o)
 	pw_log_debug("switching to %s", name);
 
 	{
-		char encoded[1024];
-		spa_json_encode_string(encoded, sizeof(encoded), name);
-		pw_manager_set_metadata(d->manager, d->metadata_default,
-				PW_ID_CORE,
-				pw_manager_object_is_sink(o) ? METADATA_CONFIG_DEFAULT_SINK
-					: METADATA_CONFIG_DEFAULT_SOURCE,
-				"Spa:String:JSON", "{ \"name\" %s }", encoded);
+		struct spa_json_builder b;
+		char *val;
+		size_t val_size;
+
+		if (spa_json_builder_memstream(&b, &val, &val_size, 0) >= 0) {
+			spa_json_builder_array_push(&b,  "{");
+			spa_json_builder_object_string(&b, "name", name);
+			spa_json_builder_pop(&b,         "}");
+			spa_json_builder_close(&b);
+
+			pw_manager_set_metadata(d->manager, d->metadata_default,
+					PW_ID_CORE,
+					pw_manager_object_is_sink(o) ? METADATA_CONFIG_DEFAULT_SINK
+						: METADATA_CONFIG_DEFAULT_SOURCE,
+					"Spa:String:JSON", "%s", val);
+			free(val);
+		}
 	}
 }
 
diff --git a/src/modules/module-protocol-pulse/modules/module-tunnel-sink.c b/src/modules/module-protocol-pulse/modules/module-tunnel-sink.c
index 59de3c6c2..7c34b5f6b 100644
--- a/src/modules/module-protocol-pulse/modules/module-tunnel-sink.c
+++ b/src/modules/module-protocol-pulse/modules/module-tunnel-sink.c
@@ -4,7 +4,7 @@
 
 #include <spa/param/audio/format-utils.h>
 #include <spa/utils/hook.h>
-#include <spa/utils/json.h>
+#include <spa/utils/json-builder.h>
 
 #include <pipewire/pipewire.h>
 #include <pipewire/i18n.h>
@@ -70,22 +70,24 @@ static const struct pw_impl_module_events module_events = {
 static int module_tunnel_sink_load(struct module *module)
 {
 	struct module_tunnel_sink_data *data = module->user_data;
-	FILE *f;
+	struct spa_json_builder b;
 	char *args;
 	size_t size;
+	int res;
 
 	pw_properties_setf(data->stream_props, "pulse.module.id",
 			"%u", module->index);
 
-	if ((f = open_memstream(&args, &size)) == NULL)
-		return -errno;
+	if ((res = spa_json_builder_memstream(&b, &args, &size, 0)) < 0)
+		return res;
 
-	fprintf(f, "{");
-	pw_properties_serialize_dict(f, &module->props->dict, 0);
-	fprintf(f, " stream.props = {");
-	pw_properties_serialize_dict(f, &data->stream_props->dict, 0);
-	fprintf(f, " } }");
-	fclose(f);
+	spa_json_builder_array_push(&b, "{");
+	pw_properties_serialize_dict(b.f, &module->props->dict, 0);
+	spa_json_builder_object_push(&b,  "stream.props", "{");
+	pw_properties_serialize_dict(b.f, &data->stream_props->dict, 0);
+	spa_json_builder_pop(&b,          "}");
+	spa_json_builder_pop(&b,        "}");
+	spa_json_builder_close(&b);
 
 	data->mod = pw_context_load_module(module->impl->context,
 			"libpipewire-module-pulse-tunnel",
diff --git a/src/modules/module-protocol-pulse/modules/module-tunnel-source.c b/src/modules/module-protocol-pulse/modules/module-tunnel-source.c
index 415f2ddd1..af6a29d87 100644
--- a/src/modules/module-protocol-pulse/modules/module-tunnel-source.c
+++ b/src/modules/module-protocol-pulse/modules/module-tunnel-source.c
@@ -4,7 +4,7 @@
 
 #include <spa/param/audio/format-utils.h>
 #include <spa/utils/hook.h>
-#include <spa/utils/json.h>
+#include <spa/utils/json-builder.h>
 
 #include <pipewire/pipewire.h>
 #include <pipewire/i18n.h>
@@ -70,22 +70,24 @@ static const struct pw_impl_module_events module_events = {
 static int module_tunnel_source_load(struct module *module)
 {
 	struct module_tunnel_source_data *data = module->user_data;
-	FILE *f;
+	struct spa_json_builder b;
 	char *args;
 	size_t size;
+	int res;
 
 	pw_properties_setf(data->stream_props, "pulse.module.id",
 			"%u", module->index);
 
-	if ((f = open_memstream(&args, &size)) == NULL)
-		return -errno;
+	if ((res = spa_json_builder_memstream(&b, &args, &size, 0)) < 0)
+		return res;
 
-	fprintf(f, "{");
-	pw_properties_serialize_dict(f, &module->props->dict, 0);
-	fprintf(f, " stream.props = {");
-	pw_properties_serialize_dict(f, &data->stream_props->dict, 0);
-	fprintf(f, " } }");
-	fclose(f);
+	spa_json_builder_array_push(&b, "{");
+	pw_properties_serialize_dict(b.f, &module->props->dict, 0);
+	spa_json_builder_object_push(&b,  "stream.props", "{");
+	pw_properties_serialize_dict(b.f, &data->stream_props->dict, 0);
+	spa_json_builder_pop(&b,          "}");
+	spa_json_builder_pop(&b,        "}");
+	spa_json_builder_close(&b);
 
 	data->mod = pw_context_load_module(module->impl->context,
 			"libpipewire-module-pulse-tunnel",
diff --git a/src/modules/module-protocol-pulse/modules/module-virtual-sink.c b/src/modules/module-protocol-pulse/modules/module-virtual-sink.c
index e3193f2f6..66e196169 100644
--- a/src/modules/module-protocol-pulse/modules/module-virtual-sink.c
+++ b/src/modules/module-protocol-pulse/modules/module-virtual-sink.c
@@ -4,7 +4,7 @@
 
 #include <spa/param/audio/format-utils.h>
 #include <spa/utils/hook.h>
-#include <spa/utils/json.h>
+#include <spa/utils/json-builder.h>
 #include <pipewire/pipewire.h>
 
 #include "../defs.h"
@@ -66,26 +66,29 @@ static const struct pw_impl_module_events module_events = {
 static int module_virtual_sink_load(struct module *module)
 {
 	struct module_virtual_sink_data *data = module->user_data;
-	FILE *f;
+	struct spa_json_builder b;
 	char *args;
 	size_t size;
+	int res;
 
 	pw_properties_setf(data->capture_props, PW_KEY_NODE_GROUP, "virtual-sink-%u", module->index);
 	pw_properties_setf(data->playback_props, PW_KEY_NODE_GROUP, "virtual-sink-%u", module->index);
 	pw_properties_setf(data->capture_props, "pulse.module.id", "%u", module->index);
 	pw_properties_setf(data->playback_props, "pulse.module.id", "%u", module->index);
 
-	if ((f = open_memstream(&args, &size)) == NULL)
-		return -errno;
+	if ((res = spa_json_builder_memstream(&b, &args, &size, 0)) < 0)
+		return res;
 
-	fprintf(f, "{");
-	pw_properties_serialize_dict(f, &data->global_props->dict, 0);
-	fprintf(f, " capture.props = {");
-	pw_properties_serialize_dict(f, &data->capture_props->dict, 0);
-	fprintf(f, " } playback.props = {");
-	pw_properties_serialize_dict(f, &data->playback_props->dict, 0);
-	fprintf(f, " } }");
-	fclose(f);
+	spa_json_builder_array_push(&b, "{");
+	pw_properties_serialize_dict(b.f, &data->global_props->dict, 0);
+	spa_json_builder_object_push(&b,  "capture.props", "{");
+	pw_properties_serialize_dict(b.f, &data->capture_props->dict, 0);
+	spa_json_builder_pop(&b,          "}");
+	spa_json_builder_object_push(&b,  "playback.props", "{");
+	pw_properties_serialize_dict(b.f, &data->playback_props->dict, 0);
+	spa_json_builder_pop(&b,          "}");
+	spa_json_builder_pop(&b,        "}");
+	spa_json_builder_close(&b);
 
 	data->mod = pw_context_load_module(module->impl->context,
 			"libpipewire-module-loopback",
diff --git a/src/modules/module-protocol-pulse/modules/module-virtual-source.c b/src/modules/module-protocol-pulse/modules/module-virtual-source.c
index fe3f10648..da6947e45 100644
--- a/src/modules/module-protocol-pulse/modules/module-virtual-source.c
+++ b/src/modules/module-protocol-pulse/modules/module-virtual-source.c
@@ -5,7 +5,7 @@
 
 #include <spa/param/audio/format-utils.h>
 #include <spa/utils/hook.h>
-#include <spa/utils/json.h>
+#include <spa/utils/json-builder.h>
 #include <pipewire/pipewire.h>
 
 #include "../defs.h"
@@ -68,26 +68,29 @@ static const struct pw_impl_module_events module_events = {
 static int module_virtual_source_load(struct module *module)
 {
 	struct module_virtual_source_data *data = module->user_data;
-	FILE *f;
+	struct spa_json_builder b;
 	char *args;
 	size_t size;
+	int res;
 
 	pw_properties_setf(data->capture_props, PW_KEY_NODE_GROUP, "virtual-source-%u", module->index);
 	pw_properties_setf(data->playback_props, PW_KEY_NODE_GROUP, "virtual-source-%u", module->index);
 	pw_properties_setf(data->capture_props, "pulse.module.id", "%u", module->index);
 	pw_properties_setf(data->playback_props, "pulse.module.id", "%u", module->index);
 
-	if ((f = open_memstream(&args, &size)) == NULL)
-		return -errno;
+	if ((res = spa_json_builder_memstream(&b, &args, &size, 0)) < 0)
+		return res;
 
-	fprintf(f, "{");
-	pw_properties_serialize_dict(f, &data->global_props->dict, 0);
-	fprintf(f, " capture.props = {");
-	pw_properties_serialize_dict(f, &data->capture_props->dict, 0);
-	fprintf(f, " } playback.props = {");
-	pw_properties_serialize_dict(f, &data->playback_props->dict, 0);
-	fprintf(f, " } }");
-	fclose(f);
+	spa_json_builder_array_push(&b, "{");
+	pw_properties_serialize_dict(b.f, &data->global_props->dict, 0);
+	spa_json_builder_object_push(&b,  "capture.props", "{");
+	pw_properties_serialize_dict(b.f, &data->capture_props->dict, 0);
+	spa_json_builder_pop(&b,          "}");
+	spa_json_builder_object_push(&b,  "playback.props", "{");
+	pw_properties_serialize_dict(b.f, &data->playback_props->dict, 0);
+	spa_json_builder_pop(&b,          "}");
+	spa_json_builder_pop(&b,        "}");
+	spa_json_builder_close(&b);
 
 	data->mod = pw_context_load_module(module->impl->context,
 			"libpipewire-module-loopback",
diff --git a/src/modules/module-protocol-pulse/modules/module-x11-bell.c b/src/modules/module-protocol-pulse/modules/module-x11-bell.c
index b9d7c4908..9ae13d915 100644
--- a/src/modules/module-protocol-pulse/modules/module-x11-bell.c
+++ b/src/modules/module-protocol-pulse/modules/module-x11-bell.c
@@ -2,7 +2,7 @@
 /* SPDX-FileCopyrightText: Copyright © 2022 Wim Taymans <wim.taymans@gmail.com> */
 /* SPDX-License-Identifier: MIT */
 
-#include <spa/utils/json.h>
+#include <spa/utils/json-builder.h>
 #include <pipewire/pipewire.h>
 
 #include "../module.h"
@@ -56,34 +56,26 @@ static const struct pw_impl_module_events module_events = {
 static int module_x11_bell_load(struct module *module)
 {
 	struct module_x11_bell_data *data = module->user_data;
-	FILE *f;
+	struct spa_json_builder b;
 	char *args;
 	const char *str;
-	char encoded[1024];
 	size_t size;
+	int res;
 
-	if ((f = open_memstream(&args, &size)) == NULL)
-		return -errno;
+	if ((res = spa_json_builder_memstream(&b, &args, &size, 0)) < 0)
+		return res;
 
-	fprintf(f, "{");
-	if ((str = pw_properties_get(module->props, "sink")) != NULL) {
-		spa_json_encode_string(encoded, sizeof(encoded), str);
-		fprintf(f, " sink.name = %s", encoded);
-	}
-	if ((str = pw_properties_get(module->props, "sample")) != NULL) {
-		spa_json_encode_string(encoded, sizeof(encoded), str);
-		fprintf(f, " sample.name = %s", encoded);
-	}
-	if ((str = pw_properties_get(module->props, "display")) != NULL) {
-		spa_json_encode_string(encoded, sizeof(encoded), str);
-		fprintf(f, " x11.display = %s", encoded);
-	}
-	if ((str = pw_properties_get(module->props, "xauthority")) != NULL) {
-		spa_json_encode_string(encoded, sizeof(encoded), str);
-		fprintf(f, " x11.xauthority = %s", encoded);
-	}
-	fprintf(f, " }");
-	fclose(f);
+	spa_json_builder_array_push(&b, "{");
+	if ((str = pw_properties_get(module->props, "sink")) != NULL)
+		spa_json_builder_object_string(&b, "sink.name", str);
+	if ((str = pw_properties_get(module->props, "sample")) != NULL)
+		spa_json_builder_object_string(&b, "sample.name", str);
+	if ((str = pw_properties_get(module->props, "display")) != NULL)
+		spa_json_builder_object_string(&b, "x11.display", str);
+	if ((str = pw_properties_get(module->props, "xauthority")) != NULL)
+		spa_json_builder_object_string(&b, "x11.xauthority", str);
+	spa_json_builder_pop(&b,        "}");
+	spa_json_builder_close(&b);
 
 	data->mod = pw_context_load_module(module->impl->context,
 			"libpipewire-module-x11-bell",
diff --git a/src/modules/module-protocol-pulse/modules/module-zeroconf-discover.c b/src/modules/module-protocol-pulse/modules/module-zeroconf-discover.c
index 5b1763eb8..b2b3acec9 100644
--- a/src/modules/module-protocol-pulse/modules/module-zeroconf-discover.c
+++ b/src/modules/module-protocol-pulse/modules/module-zeroconf-discover.c
@@ -3,6 +3,7 @@
 /* SPDX-License-Identifier: MIT */
 
 #include <spa/utils/hook.h>
+#include <spa/utils/json-builder.h>
 #include <pipewire/pipewire.h>
 
 #include "../defs.h"
@@ -57,18 +58,19 @@ static const struct pw_impl_module_events module_events = {
 static int module_zeroconf_discover_load(struct module *module)
 {
 	struct module_zeroconf_discover_data *data = module->user_data;
-	FILE *f;
+	struct spa_json_builder b;
 	char *args;
 	size_t size;
+	int res;
 
-	if ((f = open_memstream(&args, &size)) == NULL)
-		return -errno;
+	if ((res = spa_json_builder_memstream(&b, &args, &size, 0)) < 0)
+		return res;
 
-	fprintf(f, "{");
+	spa_json_builder_array_push(&b, "{");
 	if (data->latency_msec > 0)
-		fprintf(f, " pulse.latency = %u ", data->latency_msec);
-	fprintf(f, "}");
-	fclose(f);
+		spa_json_builder_object_uint(&b, "pulse.latency", data->latency_msec);
+	spa_json_builder_pop(&b,        "}");
+	spa_json_builder_close(&b);
 
 	data->mod = pw_context_load_module(module->impl->context,
 			"libpipewire-module-zeroconf-discover",
diff --git a/src/modules/module-protocol-pulse/pulse-server.c b/src/modules/module-protocol-pulse/pulse-server.c
index 5191dd6b4..eea6693c3 100644
--- a/src/modules/module-protocol-pulse/pulse-server.c
+++ b/src/modules/module-protocol-pulse/pulse-server.c
@@ -27,7 +27,7 @@
 #include <spa/param/audio/format-utils.h>
 #include <spa/param/props.h>
 #include <spa/utils/ringbuffer.h>
-#include <spa/utils/json.h>
+#include <spa/utils/json-builder.h>
 #include <spa/utils/overflow.h>
 
 #include <pipewire/pipewire.h>
@@ -4818,12 +4818,23 @@ static int do_set_default(struct client *client, uint32_t command, uint32_t tag,
 		else if (spa_strendswith(name, ".monitor"))
 			name = strndupa(name, strlen(name)-8);
 
-		char val[1024];
-		spa_json_encode_string(val, sizeof(val), name);
+		struct spa_json_builder b;
+		char *val;
+		size_t val_size;
+
+		if ((res = spa_json_builder_memstream(&b, &val, &val_size, 0)) < 0)
+			return res;
+
+		spa_json_builder_array_push(&b, "{");
+		spa_json_builder_object_string(&b, "name", name);
+		spa_json_builder_pop(&b,        "}");
+		spa_json_builder_close(&b);
+
 		res = pw_manager_set_metadata(manager, client->metadata_default,
 				PW_ID_CORE,
 				sink ? METADATA_CONFIG_DEFAULT_SINK : METADATA_CONFIG_DEFAULT_SOURCE,
-				"Spa:String:JSON", "{ \"name\": %s }", val);
+				"Spa:String:JSON", "%s", val);
+		free(val);
 	} else {
 		res = pw_manager_set_metadata(manager, client->metadata_default,
 				PW_ID_CORE,
diff --git a/src/modules/module-protocol-simple.c b/src/modules/module-protocol-simple.c
index ffc225b98..3a405684d 100644
--- a/src/modules/module-protocol-simple.c
+++ b/src/modules/module-protocol-simple.c
@@ -21,7 +21,7 @@
 
 #include <spa/utils/result.h>
 #include <spa/utils/string.h>
-#include <spa/utils/json.h>
+#include <spa/utils/json-builder.h>
 #include <spa/pod/pod.h>
 #include <spa/pod/builder.h>
 #include <spa/debug/types.h>
@@ -961,7 +961,7 @@ int pipewire__module_init(struct pw_impl_module *module, const char *args)
 	struct pw_properties *props;
 	struct impl *impl;
 	struct server *s;
-	FILE *f;
+	struct spa_json_builder b;
 	char *str;
 	size_t size;
 	int res;
@@ -994,13 +994,12 @@ int pipewire__module_init(struct pw_impl_module *module, const char *args)
 	if ((res = parse_params(impl)) < 0)
 		goto error_free;
 
-	if ((f = open_memstream(&str, &size)) == NULL) {
-		res = -errno;
+	if ((res = spa_json_builder_memstream(&b, &str, &size, 0)) < 0) {
 		pw_log_error("Can't open memstream: %m");
 		goto error_free;
 	}
 
-	fprintf(f, "[");
+	spa_json_builder_array_push(&b, "[");
 
 	spa_list_for_each(s, &impl->server_list, link) {
 		char ip[128];
@@ -1010,10 +1009,11 @@ int pipewire__module_init(struct pw_impl_module *module, const char *args)
 		if (pw_net_get_ip(&s->addr, ip, sizeof(ip), &ipv4, &port) < 0)
 			continue;
 
-		fprintf(f, " \"%s%s%s:%d\"", ipv4 ? "" : "[", ip, ipv4 ? "" : "]", port);
+		spa_json_builder_array_stringf(&b, "%s%s%s:%d",
+				ipv4 ? "" : "[", ip, ipv4 ? "" : "]", port);
 	}
-	fprintf(f, " ]");
-	fclose(f);
+	spa_json_builder_pop(&b, "]");
+	spa_json_builder_close(&b);
 
 	pw_log_info("listening on %s", str);
 	it[0] = SPA_DICT_ITEM_INIT("server.address", str);
diff --git a/src/modules/module-raop-discover.c b/src/modules/module-raop-discover.c
index 60bdfa563..33ec653e8 100644
--- a/src/modules/module-raop-discover.c
+++ b/src/modules/module-raop-discover.c
@@ -14,7 +14,7 @@
 
 #include <spa/utils/result.h>
 #include <spa/utils/string.h>
-#include <spa/utils/json.h>
+#include <spa/utils/json-builder.h>
 
 #include <pipewire/impl.h>
 #include <pipewire/i18n.h>
@@ -232,22 +232,21 @@ struct match_info {
 static int create_stream(struct impl *impl, struct pw_properties *props,
 		struct tunnel *t)
 {
-	FILE *f;
+	struct spa_json_builder b;
 	char *args;
 	size_t size;
 	int res = 0;
 	struct pw_impl_module *mod;
 
-	if ((f = open_memstream(&args, &size)) == NULL) {
-		res = -errno;
+	if ((res = spa_json_builder_memstream(&b, &args, &size, 0)) < 0) {
 		pw_log_error("Can't open memstream: %m");
 		goto done;
 	}
 
-	fprintf(f, "{");
-	pw_properties_serialize_dict(f, &props->dict, 0);
-	fprintf(f, "}");
-        fclose(f);
+	spa_json_builder_array_push(&b, "{");
+	pw_properties_serialize_dict(b.f, &props->dict, 0);
+	spa_json_builder_pop(&b,        "}");
+	spa_json_builder_close(&b);
 
 	pw_log_info("loading module args:'%s'", args);
 	mod = pw_context_load_module(impl->context,
diff --git a/src/modules/module-rtp-sap.c b/src/modules/module-rtp-sap.c
index a8c1fc5e5..c1292ca20 100644
--- a/src/modules/module-rtp-sap.c
+++ b/src/modules/module-rtp-sap.c
@@ -18,7 +18,7 @@
 #include <spa/utils/cleanup.h>
 #include <spa/utils/hook.h>
 #include <spa/utils/result.h>
-#include <spa/utils/json.h>
+#include <spa/utils/json-builder.h>
 #include <spa/debug/types.h>
 
 #include <pipewire/pipewire.h>
@@ -1269,37 +1269,34 @@ static int session_load_source(struct session *session, struct pw_properties *pr
 {
 	struct impl *impl = session->impl;
 	struct pw_context *context = pw_impl_module_get_context(impl->module);
-	FILE *f = NULL;
+	struct spa_json_builder b;
 	char *args = NULL;
 	size_t size;
 	const char *str, *media;
 	int res;
 
-	if ((f = open_memstream(&args, &size)) == NULL) {
-		res = -errno;
+	if ((res = spa_json_builder_memstream(&b, &args, &size, 0)) < 0) {
 		pw_log_error("Can't open memstream: %m");
-		goto done;
+		return res;
 	}
-	fprintf(f, "{");
+	spa_json_builder_array_push(&b, "{");
 
 	if ((str = pw_properties_get(props, "rtp.destination.ip")) != NULL)
-		fprintf(f, "\"source.ip\" = \"%s\", ", str);
+		spa_json_builder_object_string(&b, "source.ip", str);
 	if ((str = pw_properties_get(props, "rtp.destination.port")) != NULL)
-		fprintf(f, "\"source.port\" = %s, ", str);
+		spa_json_builder_object_value(&b, false, "source.port", str);
 	if ((str = pw_properties_get(props, "rtp.session")) != NULL)
-		fprintf(f, "\"sess.name\" = \"%s\", ", str);
+		spa_json_builder_object_string(&b, "sess.name", str);
 
 	/* Use an interface if explicitly specified, else use the SAP interface if that was specified */
-	if ((str = pw_properties_get(props, "local.ifname")) != NULL || (str = impl->ifname) != NULL) {
-		fprintf(f, "\"local.ifname\" = \"%s\", ", str);
-	}
+	if ((str = pw_properties_get(props, "local.ifname")) != NULL || (str = impl->ifname) != NULL)
+		spa_json_builder_object_string(&b, "local.ifname", str);
 
 	if ((media = pw_properties_get(props, "sess.media")) == NULL)
 		media = "audio";
 
-	if ((str = pw_properties_get(props, "cleanup.sec")) != NULL) {
-		fprintf(f, "\"cleanup.sec\" = \"%s\", ", str);
-	}
+	if ((str = pw_properties_get(props, "cleanup.sec")) != NULL)
+		spa_json_builder_object_string(&b, "cleanup.sec", str);
 
 	if (spa_streq(media, "audio")) {
 		const char *mime;
@@ -1308,15 +1305,16 @@ static int session_load_source(struct session *session, struct pw_properties *pr
 		if ((mime = pw_properties_get(props, "rtp.mime")) == NULL) {
 			pw_log_error("missing rtp.mime property");
 			res = -EINVAL;
-			goto done;
+			goto error;
 		}
 		format_info = find_audio_format_info(mime);
 		if (format_info == NULL) {
 			pw_log_error("unknown rtp.mime type %s", mime);
 			res = -ENOTSUP;
-			goto done;
+			goto error;
 		}
-		fprintf(f, "\"sess.media\" = \"%s\", ", format_info->media_type);
+		spa_json_builder_object_string(&b, "sess.media", format_info->media_type);
+
 		if (format_info->format_str != NULL) {
 			pw_properties_set(props, "audio.format", format_info->format_str);
 			if ((str = pw_properties_get(props, "rtp.rate")) != NULL)
@@ -1325,41 +1323,40 @@ static int session_load_source(struct session *session, struct pw_properties *pr
 				pw_properties_set(props, "audio.channels", str);
 		}
 		if ((str = pw_properties_get(props, "rtp.ssrc")) != NULL)
-			fprintf(f, "\"rtp.receiver-ssrc\" = \"%s\", ", str);
+			spa_json_builder_object_string(&b, "rtp.receiver-ssrc", str);
 	} else {
 		pw_log_error("Unhandled media %s", media);
 		res = -EINVAL;
-		goto done;
+		goto error;
 	}
 	if ((str = pw_properties_get(props, "rtp.ts-offset")) != NULL)
-		fprintf(f, "\"sess.ts-offset\" = %s, ", str);
+		spa_json_builder_object_value(&b, false, "sess.ts-offset", str);
 
-	fprintf(f, " stream.props = {");
-	pw_properties_serialize_dict(f, &props->dict, 0);
-	fprintf(f, " }");
-	fprintf(f, "}");
-        fclose(f);
-	f = NULL;
+	spa_json_builder_object_push(&b, "stream.props", "{");
+	pw_properties_serialize_dict(b.f, &props->dict, 0);
+	spa_json_builder_pop(&b,         "}");
+	spa_json_builder_pop(&b,       "}");
+	spa_json_builder_close(&b);
 
 	pw_log_info("loading new RTP source");
 	session->module = pw_context_load_module(context,
 				"libpipewire-module-rtp-source",
 				args, NULL);
 
+	free(args);
+
 	if (session->module == NULL) {
-		res = -errno;
 		pw_log_error("Can't load module: %m");
-		goto done;
+		return -errno;
 	}
 
 	pw_impl_module_add_listener(session->module,
 			&session->module_listener,
 			&session_module_events, session);
 
-	res = 0;
-done:
-	if (f != NULL)
-		fclose(f);
+	return 0;
+error:
+	spa_json_builder_close(&b);
 	free(args);
 	return res;
 }
diff --git a/src/modules/module-snapcast-discover.c b/src/modules/module-snapcast-discover.c
index 5c7896bcf..677725699 100644
--- a/src/modules/module-snapcast-discover.c
+++ b/src/modules/module-snapcast-discover.c
@@ -21,7 +21,7 @@
 
 #include <spa/utils/result.h>
 #include <spa/utils/string.h>
-#include <spa/utils/json.h>
+#include <spa/utils/json-builder.h>
 #include <spa/param/audio/format.h>
 #include <spa/param/audio/raw-json.h>
 #include <spa/debug/types.h>
@@ -523,7 +523,7 @@ static int parse_audio_info(struct pw_properties *props, struct spa_audio_info_r
 static int create_stream(struct impl *impl, struct pw_properties *props,
 		struct tunnel *t)
 {
-	FILE *f;
+	struct spa_json_builder b;
 	char *args;
 	size_t size;
 	int res = 0;
@@ -548,16 +548,15 @@ static int create_stream(struct impl *impl, struct pw_properties *props,
 		goto done;
 	}
 
-	if ((f = open_memstream(&args, &size)) == NULL) {
-		res = -errno;
+	if ((res = spa_json_builder_memstream(&b, &args, &size, 0)) < 0) {
 		pw_log_error("Can't open memstream: %m");
 		goto done;
 	}
 
-	fprintf(f, "{");
-	pw_properties_serialize_dict(f, &props->dict, 0);
-	fprintf(f, "}");
-        fclose(f);
+	spa_json_builder_array_push(&b, "{");
+	pw_properties_serialize_dict(b.f, &props->dict, 0);
+	spa_json_builder_pop(&b,        "}");
+	spa_json_builder_close(&b);
 
 	pw_log_info("loading module args:'%s'", args);
 	mod = pw_context_load_module(impl->context,
diff --git a/src/modules/module-zeroconf-discover.c b/src/modules/module-zeroconf-discover.c
index 61108d424..c2dd72188 100644
--- a/src/modules/module-zeroconf-discover.c
+++ b/src/modules/module-zeroconf-discover.c
@@ -14,7 +14,7 @@
 
 #include <spa/utils/result.h>
 #include <spa/utils/string.h>
-#include <spa/utils/json.h>
+#include <spa/utils/json-builder.h>
 #include <spa/param/audio/format-utils.h>
 
 #include <pipewire/impl.h>
@@ -233,7 +233,7 @@ static void on_zeroconf_added(void *data, const void *user_data, const struct sp
 	struct tunnel *t;
 	struct tunnel_info tinfo;
 	const struct spa_dict_item *it;
-	FILE *f;
+	struct spa_json_builder b;
 	char *args;
 	size_t size;
 	struct pw_impl_module *mod;
@@ -309,17 +309,17 @@ static void on_zeroconf_added(void *data, const void *user_data, const struct sp
 	if ((str = pw_properties_get(impl->properties, "pulse.latency")) != NULL)
 		pw_properties_set(props, "pulse.latency", str);
 
-	if ((f = open_memstream(&args, &size)) == NULL) {
+	if (spa_json_builder_memstream(&b, &args, &size, 0) < 0) {
 		pw_log_error("Can't open memstream: %m");
 		goto done;
 	}
 
-	fprintf(f, "{");
-	pw_properties_serialize_dict(f, &props->dict, 0);
-	fprintf(f, " stream.props = {");
-	fprintf(f, " }");
-	fprintf(f, "}");
-        fclose(f);
+	spa_json_builder_array_push(&b, "{");
+	pw_properties_serialize_dict(b.f, &props->dict, 0);
+	spa_json_builder_object_push(&b,  "stream.props", "{");
+	spa_json_builder_pop(&b,          "}");
+	spa_json_builder_pop(&b,        "}");
+	spa_json_builder_close(&b);
 
 	pw_log_info("loading module args:'%s'", args);
 	mod = pw_context_load_module(impl->context,
diff --git a/src/tools/pw-loopback.c b/src/tools/pw-loopback.c
index 991934a37..3375beae4 100644
--- a/src/tools/pw-loopback.c
+++ b/src/tools/pw-loopback.c
@@ -15,7 +15,7 @@
 #include <spa/pod/builder.h>
 #include <spa/param/audio/format-utils.h>
 #include <spa/param/audio/raw.h>
-#include <spa/utils/json.h>
+#include <spa/utils/json-builder.h>
 #include <spa/debug/file.h>
 
 #include <pipewire/pipewire.h>
@@ -92,10 +92,10 @@ int main(int argc, char *argv[])
 	struct data data = { 0 };
 	struct pw_loop *l;
 	const char *opt_remote = NULL, *remote_name;
-	char cname[256], value[256];
+	char cname[256];
+	struct spa_json_builder b;
 	char *args;
 	size_t size;
-	FILE *f;
 	static const struct option long_options[] = {
 		{ "help",		no_argument,		NULL, 'h' },
 		{ "version",		no_argument,		NULL, 'V' },
@@ -214,42 +214,44 @@ int main(int argc, char *argv[])
 	}
 
 
-	if ((f = open_memstream(&args, &size)) == NULL) {
+	if ((res = spa_json_builder_memstream(&b, &args, &size, 0)) < 0) {
 		fprintf(stderr, "can't open memstream: %m\n");
 		goto exit;
 	}
 
-	fprintf(f, "{");
-
 	remote_name = "[" PW_DEFAULT_REMOTE "-manager," PW_DEFAULT_REMOTE "]";
 	if (opt_remote)
 		remote_name = opt_remote;
 
-	fprintf(f, " remote.name = \"%s\"", remote_name);
+	spa_json_builder_array_push(&b, "{");
+
+	spa_json_builder_object_string(&b, "remote.name", remote_name);
 
 	if (data.latency != 0)
-		fprintf(f, " node.latency = %u/%u", data.latency, DEFAULT_RATE);
+		spa_json_builder_object_stringf(&b, "node.latency", "%u/%u",
+				data.latency, DEFAULT_RATE);
 	if (data.delay != 0.0f)
-		fprintf(f, " target.delay.sec = %s",
-				spa_json_format_float(value, sizeof(value), data.delay));
+		spa_json_builder_object_double(&b, "target.delay.sec", data.delay);
 	if (data.channels != 0)
-		fprintf(f, " audio.channels = %u", data.channels);
+		spa_json_builder_object_uint(&b, "audio.channels", data.channels);
 	if (data.opt_channel_map != NULL)
-		fprintf(f, " audio.position = %s", data.opt_channel_map);
+		spa_json_builder_object_value(&b, true, "audio.position", data.opt_channel_map);
 	if (data.opt_node_name != NULL)
-		fprintf(f, " node.name = %s", data.opt_node_name);
+		spa_json_builder_object_string(&b, "node.name", data.opt_node_name);
 
 	if (data.opt_group_name != NULL) {
 		pw_properties_set(data.capture_props, PW_KEY_NODE_GROUP, data.opt_group_name);
 		pw_properties_set(data.playback_props, PW_KEY_NODE_GROUP, data.opt_group_name);
 	}
 
-	fprintf(f, " capture.props = {");
-	pw_properties_serialize_dict(f, &data.capture_props->dict, 0);
-	fprintf(f, " } playback.props = {");
-	pw_properties_serialize_dict(f, &data.playback_props->dict, 0);
-	fprintf(f, " } }");
-	fclose(f);
+	spa_json_builder_object_push(&b,  "capture.props", "{");
+	pw_properties_serialize_dict(b.f, &data.capture_props->dict, 0);
+	spa_json_builder_pop(&b,          "}");
+	spa_json_builder_object_push(&b,  "playback.props", "{");
+	pw_properties_serialize_dict(b.f, &data.playback_props->dict, 0);
+	spa_json_builder_pop(&b,          "}");
+	spa_json_builder_pop(&b,        "}");
+	spa_json_builder_close(&b);
 
 	pw_log_info("loading module with %s", args);