diff --git a/lib/compat/wordpress-6.1/class-wp-theme-json-data.php b/lib/compat/wordpress-6.1/class-wp-theme-json-data.php
new file mode 100644
index 0000000000000..d03b2227558ea
--- /dev/null
+++ b/lib/compat/wordpress-6.1/class-wp-theme-json-data.php
@@ -0,0 +1,60 @@
+<?php
+/**
+ * API to update a theme.json structure.
+ *
+ * @package gutenberg
+ */
+
+/**
+ * Class to update with a theme.json structure.
+ */
+class WP_Theme_JSON_Data {
+
+	/**
+	 * Container of the data to update.
+	 *
+	 * @var WP_Theme_JSON
+	 */
+	private $theme_json = null;
+
+	/**
+	 * The origin of the data: default, theme, user, etc.
+	 *
+	 * @var string
+	 */
+	private $origin = null;
+
+	/**
+	 * Constructor.
+	 *
+	 * @param array  $data   Array following the theme.json specification.
+	 * @param string $origin The origin of the data: default, theme, user.
+	 */
+	public function __construct( $data = array(), $origin = 'theme' ) {
+		$this->origin     = $origin;
+		$this->theme_json = new WP_Theme_JSON_Gutenberg( $data, $this->origin );
+	}
+
+	/**
+	 * Updates the theme.json with the the given data.
+	 *
+	 * @param array $new_data Array following the theme.json specification.
+	 *
+	 * @return WP_Theme_JSON_Data the modified data.
+	 */
+	public function update_with( $new_data ) {
+		$this->theme_json->merge( new WP_Theme_JSON_Gutenberg( $new_data, $this->origin ) );
+
+		return $this;
+	}
+
+	/**
+	 * Returns the underlying data.
+	 *
+	 * @return array
+	 */
+	public function get_data() {
+		return $this->theme_json->get_raw_data();
+	}
+
+}
diff --git a/lib/compat/wordpress-6.1/class-wp-theme-json-resolver-6-1.php b/lib/compat/wordpress-6.1/class-wp-theme-json-resolver-6-1.php
index f704daaffafb1..d210fa16d2310 100644
--- a/lib/compat/wordpress-6.1/class-wp-theme-json-resolver-6-1.php
+++ b/lib/compat/wordpress-6.1/class-wp-theme-json-resolver-6-1.php
@@ -56,8 +56,50 @@ public static function get_core_data() {
 
 		$config       = static::read_json_file( __DIR__ . '/theme.json' );
 		$config       = static::translate( $config );
-		static::$core = new WP_Theme_JSON_Gutenberg( $config, 'default' );
+		$config       = apply_filters( 'global_styles_default', new WP_Theme_JSON_Data( $config, 'default' ) );
+		static::$core = new WP_Theme_JSON_Gutenberg( $config->get_data(), 'default' );
 
 		return static::$core;
 	}
+
+	/**
+	 * Returns the user's origin config.
+	 *
+	 * @return WP_Theme_JSON_Gutenberg Entity that holds styles for user data.
+	 */
+	public static function get_user_data() {
+		if ( null !== static::$user ) {
+			return static::$user;
+		}
+
+		$config   = array();
+		$user_cpt = static::get_user_data_from_wp_global_styles( wp_get_theme() );
+
+		if ( array_key_exists( 'post_content', $user_cpt ) ) {
+			$decoded_data = json_decode( $user_cpt['post_content'], true );
+
+			$json_decoding_error = json_last_error();
+			if ( JSON_ERROR_NONE !== $json_decoding_error ) {
+				trigger_error( 'Error when decoding a theme.json schema for user data. ' . json_last_error_msg() );
+				$config = apply_filters( 'global_styles_user', new WP_Theme_JSON_Data( $config, 'custom' ) );
+				return new WP_Theme_JSON_Gutenberg( $config->get_data(), 'custom' );
+			}
+
+			// Very important to verify if the flag isGlobalStylesUserThemeJSON is true.
+			// If is not true the content was not escaped and is not safe.
+			if (
+				is_array( $decoded_data ) &&
+				isset( $decoded_data['isGlobalStylesUserThemeJSON'] ) &&
+				$decoded_data['isGlobalStylesUserThemeJSON']
+			) {
+				unset( $decoded_data['isGlobalStylesUserThemeJSON'] );
+				$config = $decoded_data;
+			}
+		}
+
+		$config       = apply_filters( 'global_styles_user', new WP_Theme_JSON_Data( $config, 'custom' ) );
+		static::$user = new WP_Theme_JSON_Gutenberg( $config->get_data(), 'custom' );
+
+		return static::$user;
+	}
 }
diff --git a/lib/experimental/class-wp-theme-json-resolver-gutenberg.php b/lib/experimental/class-wp-theme-json-resolver-gutenberg.php
index 138f9b8b865b4..30b93d85e698e 100644
--- a/lib/experimental/class-wp-theme-json-resolver-gutenberg.php
+++ b/lib/experimental/class-wp-theme-json-resolver-gutenberg.php
@@ -38,7 +38,9 @@ public static function get_theme_data( $deprecated = array(), $settings = array(
 			$theme_json_data = static::read_json_file( static::get_file_path_from_theme( 'theme.json' ) );
 			$theme_json_data = static::translate( $theme_json_data, wp_get_theme()->get( 'TextDomain' ) );
 			$theme_json_data = gutenberg_add_registered_webfonts_to_theme_json( $theme_json_data );
-			static::$theme   = new WP_Theme_JSON_Gutenberg( $theme_json_data );
+
+			$theme_json_data = apply_filters( 'global_styles_theme', new WP_Theme_JSON_Data( $theme_json_data, 'theme' ) );
+			static::$theme   = new WP_Theme_JSON_Gutenberg( $theme_json_data->get_data() );
 
 			if ( wp_get_theme()->parent() ) {
 				// Get parent theme.json.
@@ -128,9 +130,11 @@ public static function get_block_data() {
 			}
 		}
 
+		$config = apply_filters( 'global_styles_blocks', new WP_Theme_JSON_Data( $config, 'core' ) );
+
 		// Core here means it's the lower level part of the styles chain.
 		// It can be a core or a third-party block.
-		return new WP_Theme_JSON_Gutenberg( $config, 'core' );
+		return new WP_Theme_JSON_Gutenberg( $config->get_data(), 'core' );
 	}
 
 	/**
diff --git a/lib/load.php b/lib/load.php
index 367e24fdc5e51..81a63b49769b6 100644
--- a/lib/load.php
+++ b/lib/load.php
@@ -83,6 +83,7 @@ function gutenberg_is_experiment_enabled( $name ) {
 require __DIR__ . '/compat/wordpress-6.1/block-editor-settings.php';
 require __DIR__ . '/compat/wordpress-6.1/persisted-preferences.php';
 require __DIR__ . '/compat/wordpress-6.1/get-global-styles-and-settings.php';
+require __DIR__ . '/compat/wordpress-6.1/class-wp-theme-json-data.php';
 require __DIR__ . '/compat/wordpress-6.1/class-wp-theme-json-6-1.php';
 require __DIR__ . '/compat/wordpress-6.1/class-wp-theme-json-resolver-6-1.php';
 require __DIR__ . '/compat/wordpress-6.1/block-template-utils.php';