diff --git a/tools/gtk-json-format.c b/tools/gtk-json-format.c
new file mode 100644
index 0000000000..9187b08039
--- /dev/null
+++ b/tools/gtk-json-format.c
@@ -0,0 +1,350 @@
+/* gtk-json-format - Formats JSON data
+ * 
+ * Copyright © 2013  Emmanuele Bassi
+ *             2021  Benjamin Otte
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library. If not, see <http://www.gnu.org/licenses/>.
+ *
+ * Author:
+ *   Emmanuele Bassi  <ebassi@gnome.org>
+ *   Benjamin Otte    <otte@gnome.org>
+ */
+
+#include "config.h"
+
+#ifdef G_OS_UNIX
+#include <unistd.h>
+#include <sys/types.h>
+#include <sys/stat.h>
+#include <gio/gunixoutputstream.h>
+#endif
+#include <fcntl.h>
+#ifdef G_OS_WIN32
+#include <windows.h>
+#endif
+
+#include <stdlib.h>
+#include <locale.h>
+
+#include <gio/gio.h>
+#include <glib/gi18n.h>
+#include <glib/gstdio.h>
+
+#include "gtk/json/gtkjsonparserprivate.h"
+#include "gtk/json/gtkjsonprinterprivate.h"
+
+#if defined (G_OS_WIN32) && !defined (HAVE_UNISTD_H)
+#include <io.h>
+
+#define STDOUT_FILENO 1
+#endif
+
+static char **files = NULL;
+static char *output = NULL;
+static gboolean ascii = FALSE;
+static gboolean prettify = FALSE;
+static int indent_spaces = 2;
+
+static GOptionEntry entries[] = {
+  { "prettify", 'p', 0, G_OPTION_ARG_NONE, &prettify, N_("Prettify output"), NULL },
+  { "indent-spaces", 'i', 0, G_OPTION_ARG_INT, &indent_spaces, N_("Indentation spaces"), N_("SPACES") },
+  { "ascii", 0, 0, G_OPTION_ARG_NONE, &ascii, N_("Convert to ASCII instead of UTF-8"), NULL },
+  { "output", 'o', 0, G_OPTION_ARG_FILENAME, &output, N_("Output file"), N_("FILE") },
+  { G_OPTION_REMAINING, 0, 0, G_OPTION_ARG_FILENAME_ARRAY, &files, NULL, N_("FILE…") },
+  { NULL },
+};
+
+typedef struct
+{
+  gchar buffer[4096];
+  gsize size;
+  int fd;
+  gboolean close;
+  int error;
+} Writer;
+
+static void
+writer_init (Writer   *writer,
+             int       fd,
+             gboolean  close)
+{
+  writer->size = 0;
+  writer->fd = fd;
+  writer->close = close;
+  writer->error = 0;
+}
+
+static void
+writer_flush (Writer     *writer,
+              const char *data,
+              gsize       len)
+{
+  if (writer->error)
+    return;
+
+again:
+  if (write (writer->fd, data, len) < 0)
+    {
+      if (errno == EINTR)
+        goto again;
+      writer->error = errno;
+    }
+}
+
+static int
+writer_finish (Writer *writer)
+{
+  writer_flush (writer, writer->buffer, writer->size);
+
+  if (writer->close)
+    g_close (writer->fd, NULL);
+
+  return writer->error;
+}
+
+static void
+writer_write (GtkJsonPrinter *printer,
+              const char     *s,
+              gpointer        data)
+{
+  Writer *writer = data;
+  int len = strlen (s);
+
+  if (sizeof (writer->buffer) - writer->size < len)
+    {
+      writer_flush (writer, writer->buffer, writer->size);
+      writer->size = 0;
+    }
+
+  if (sizeof (writer->buffer) <= len)
+    {
+      writer_flush (writer, s, len);
+      return;
+    }
+
+  memcpy (writer->buffer + writer->size, s, len);
+  writer->size += len;
+}
+
+static void
+parse_and_print (GtkJsonParser  *parser,
+                 GtkJsonPrinter *printer)
+{
+  while (TRUE)
+    {
+      char *name = gtk_json_parser_get_member_name (parser);
+
+      switch (gtk_json_parser_get_node (parser))
+        {
+        case GTK_JSON_NONE:
+          if (gtk_json_printer_get_depth (printer) == 0)
+            return;
+          gtk_json_printer_end (printer);
+          gtk_json_parser_end (parser);
+          break;
+
+        case GTK_JSON_NULL:
+          gtk_json_printer_add_null (printer, name);
+          break;
+
+        case GTK_JSON_BOOLEAN:
+          gtk_json_printer_add_boolean (printer,
+                                        name,
+                                        gtk_json_parser_get_boolean (parser));
+          break;
+
+        case GTK_JSON_NUMBER:
+          gtk_json_printer_add_number (printer,
+                                       name,
+                                       gtk_json_parser_get_number (parser));
+          break;
+
+        case GTK_JSON_STRING:
+          { 
+            char *s = gtk_json_parser_get_string (parser);
+            gtk_json_printer_add_string (printer, name, s);
+            g_free (s);
+          }
+          break;
+
+        case GTK_JSON_OBJECT:
+          gtk_json_printer_start_object (printer, name);
+          gtk_json_parser_start_object (parser);
+          continue;
+
+        case GTK_JSON_ARRAY:
+          gtk_json_printer_start_array (printer, name);
+          gtk_json_parser_start_array (parser);
+          continue;
+
+        default:
+          g_assert_not_reached ();
+          return;
+        }
+
+      g_free (name);
+      gtk_json_parser_next (parser);
+    }
+}
+
+static gboolean
+format (GtkJsonPrinter *printer,
+        GFile          *file)
+{
+  GBytes *bytes;
+  GtkJsonParser *parser;
+  GError *error = NULL;
+
+  error = NULL;
+
+  bytes = g_file_load_bytes (file, NULL, NULL, &error);
+  if (bytes == NULL)
+    {
+      /* Translators: the first %s is the program name, the second one
+       * is the URI of the file, the third is the error message.
+       */
+      g_printerr (_("%s: %s: error opening file: %s\n"),
+                  g_get_prgname (), g_file_get_uri (file), error->message);
+      g_error_free (error);
+      return FALSE;
+    }
+
+  parser = gtk_json_parser_new_for_bytes (bytes);
+  g_bytes_unref (bytes);
+  parse_and_print (parser, printer);
+  if (gtk_json_parser_get_error (parser))
+    {
+      char *uri = g_file_get_uri (file);
+      const GError *parser_error = gtk_json_parser_get_error (parser);
+
+      /* Translators: the first %s is the program name, the second one
+       * is the URI of the file, the third is the error message.
+       */
+      g_printerr (_("%s: %s: error parsing file: %s\n"),
+                  g_get_prgname (), uri, parser_error->message);
+      g_free (uri);
+      gtk_json_parser_free (parser);
+      return FALSE;
+    }
+
+  gtk_json_parser_free (parser);
+
+  return TRUE;
+}
+
+int
+main (int   argc,
+      char *argv[])
+{
+  GOptionContext *context = NULL;
+  GError *error = NULL;
+  GtkJsonPrinter *printer;
+  Writer writer;
+  gboolean res;
+  int sv_errno;
+  int i;
+
+  setlocale (LC_ALL, "");
+
+  bindtextdomain (GETTEXT_PACKAGE, GTK_LOCALEDIR);
+  bind_textdomain_codeset (GETTEXT_PACKAGE, "UTF-8");
+  textdomain (GETTEXT_PACKAGE);
+  
+  context = g_option_context_new (NULL);
+  /* Translators: this message will appear after the usage string */
+  /* and before the list of options.                              */
+  g_option_context_set_summary (context, _("Format JSON files."));
+  g_option_context_set_description (context, _("json-glib-format formats JSON resources."));
+  g_option_context_add_main_entries (context, entries, GETTEXT_PACKAGE);
+  g_option_context_parse (context, &argc, &argv, &error);
+  g_option_context_free (context);
+
+  if (error != NULL)
+    {
+      /* Translators: the %s is the program name. This error message
+       * means the user is calling json-glib-validate without any
+       * argument.
+       */
+      g_printerr (_("Error parsing commandline options: %s\n"), error->message);
+      g_printerr ("\n");
+      g_printerr (_("Try “%s --help” for more information."), g_get_prgname ());
+      g_printerr ("\n");
+      g_error_free (error);
+      return EXIT_FAILURE;
+    }
+
+  if (files == NULL)
+    {
+      /* Translators: the %s is the program name. This error message
+       * means the user is calling json-glib-validate without any
+       * argument.
+       */
+      g_printerr (_("%s: missing files"), g_get_prgname ());
+      g_printerr ("\n");
+      g_printerr (_("Try “%s --help” for more information."), g_get_prgname ());
+      g_printerr ("\n");
+      return EXIT_FAILURE;
+    }
+
+  if (output == NULL)
+    writer_init (&writer, STDOUT_FILENO, FALSE);
+  else
+    {
+      int fd;
+
+      fd = g_open (output, O_CREAT | O_WRONLY, 0666);
+      if (fd < 0)
+        {
+          sv_errno = errno;
+
+          g_printerr (_("%s: %s: error opening file: %s\n"),
+                      g_get_prgname (), output, g_strerror (sv_errno));
+          res = FALSE;
+          return EXIT_FAILURE;
+        }
+      writer_init (&writer, fd, TRUE);
+    }
+
+  printer = gtk_json_printer_new (writer_write,
+                                  &writer,
+                                  NULL);
+  gtk_json_printer_set_flags (printer,
+                              (prettify ? GTK_JSON_PRINTER_PRETTY : 0) |
+                              (ascii ? GTK_JSON_PRINTER_ASCII : 0));
+  gtk_json_printer_set_indentation (printer, indent_spaces);
+
+  res = TRUE;
+  i = 0;
+
+  do
+    {
+      GFile *file = g_file_new_for_commandline_arg (files[i]);
+
+      res = format (printer, file) && res;
+      g_object_unref (file);
+      writer_write (printer, "\n", &writer);
+    }
+  while (files[++i] != NULL);
+
+  sv_errno = writer_finish (&writer);
+  if (sv_errno)
+    {
+      g_printerr (_("%s: error writing: %s"), g_get_prgname (), g_strerror (sv_errno));
+      res = FALSE;
+    }
+
+  gtk_json_printer_free (printer);
+
+  return res ? EXIT_SUCCESS : EXIT_FAILURE;
+}
diff --git a/tools/meson.build b/tools/meson.build
index 0e90d88945..6f51c9b192 100644
--- a/tools/meson.build
+++ b/tools/meson.build
@@ -33,6 +33,7 @@ gtk_tools = [
                          'fake-scope.c'], [libgtk_dep] ],
   ['gtk4-update-icon-cache', ['updateiconcache.c'] + extra_update_icon_cache_objs, [ libgtk_static_dep ] ],
   ['gtk4-encode-symbolic-svg', ['encodesymbolic.c'], [ libgtk_static_dep ] ],
+  ['gtk4-json-format', ['gtk-json-format.c'], [ libgtk_json_dep ], [ libgtk_json ] ],
 ]
 
 if os_unix
@@ -43,12 +44,14 @@ foreach tool: gtk_tools
   tool_name = tool.get(0)
   tool_srcs = tool.get(1)
   tool_deps = tool.get(2)
+  tool_link = tool.get(3, [])
 
   exe = executable(tool_name,
     sources: tool_srcs,
     include_directories: [confinc],
     c_args: common_cflags,
     dependencies: tool_deps,
+    link_with: tool_link,
     install: true,
   )