diff --git a/docs/how-to-guides/themes/theme-json.md b/docs/how-to-guides/themes/theme-json.md
index 3f3da4c9f4a75..f6671698afc09 100644
--- a/docs/how-to-guides/themes/theme-json.md
+++ b/docs/how-to-guides/themes/theme-json.md
@@ -280,6 +280,14 @@ Each block can configure any of these settings separately, providing a more fine
 
 Note, however, that not all settings are relevant for all blocks. The settings section provides an opt-in/opt-out mechanism for themes, but it's the block's responsibility to add support for the features that are relevant to it. For example, if a block doesn't implement the `dropCap` feature, a theme can't enable it for such a block through `theme.json`.
 
+### Opt-in into appearance controls
+
+There's one special setting property, `appareance`, which can be a boolean and its default value is true. When this is enabled, the following setting properties will be on by default:
+
+- border: color, radius, style, width
+- spacing: margin, padding, units
+- typography: customFontSize, lineHeight
+
 #### Backward compatibility with add_theme_support
 
 To retain backward compatibility, the existing `add_theme_support` declarations that configure the block editor are retrofit in the proper categories for the top-level section. For example, if a theme uses `add_theme_support('disable-custom-colors')`, it'll be the same as setting `settings.color.custom` to `false`. If the `theme.json` contains any settings, these will take precedence over the values declared via `add_theme_support`. This is the complete list of equivalences:
diff --git a/lib/class-wp-theme-json-gutenberg.php b/lib/class-wp-theme-json-gutenberg.php
index 52d1cbbb643aa..523e65d046cc2 100644
--- a/lib/class-wp-theme-json-gutenberg.php
+++ b/lib/class-wp-theme-json-gutenberg.php
@@ -81,6 +81,7 @@ class WP_Theme_JSON_Gutenberg {
 	);
 
 	const VALID_SETTINGS = array(
+		'appearance' => null,
 		'border'     => array(
 			'color'  => null,
 			'radius' => null,
@@ -290,7 +291,8 @@ public function __construct( $theme_json = array(), $origin = 'theme' ) {
 
 		$valid_block_names   = array_keys( self::get_blocks_metadata() );
 		$valid_element_names = array_keys( self::ELEMENTS );
-		$this->theme_json    = self::sanitize( $theme_json, $valid_block_names, $valid_element_names );
+		$theme_json          = self::sanitize( $theme_json, $valid_block_names, $valid_element_names );
+		$this->theme_json    = self::maybe_opt_in_into_settings( $theme_json );
 
 		// Internally, presets are keyed by origin.
 		$nodes = self::get_setting_nodes( $this->theme_json );
@@ -305,6 +307,48 @@ public function __construct( $theme_json = array(), $origin = 'theme' ) {
 		}
 	}
 
+	/**
+	 * Enables some opt-in settings if theme declared support.
+	 *
+	 * @param array $theme_json A theme.json structure to modify.
+	 * @return array The modified theme.json structure.
+	 */
+	private static function maybe_opt_in_into_settings( $theme_json ) {
+		$new_theme_json = $theme_json;
+
+		if ( isset( $new_theme_json['settings']['appearance'] ) ) {
+			self::do_opt_in_into_settings( $new_theme_json['settings'] );
+		}
+
+		if ( isset( $new_theme_json['settings']['blocks'] ) && is_array( $new_theme_json['settings']['blocks'] ) ) {
+			foreach ( $new_theme_json['settings']['blocks'] as &$block ) {
+				if ( isset( $block['appearance'] ) ) {
+					self::do_opt_in_into_settings( $block );
+				}
+			}
+		}
+
+		return $new_theme_json;
+	}
+
+	/**
+	 * Enables some settings.
+	 *
+	 * @param array $context The context to which the settings belong.
+	 */
+	private static function do_opt_in_into_settings( &$context ) {
+		gutenberg_experimental_set( $context, array( 'border', 'color' ), true );
+		gutenberg_experimental_set( $context, array( 'border', 'radius' ), true );
+		gutenberg_experimental_set( $context, array( 'border', 'style' ), true );
+		gutenberg_experimental_set( $context, array( 'border', 'width' ), true );
+		gutenberg_experimental_set( $context, array( 'spacing', 'margin' ), true );
+		gutenberg_experimental_set( $context, array( 'spacing', 'padding' ), true );
+		gutenberg_experimental_set( $context, array( 'spacing', 'units' ), true );
+		gutenberg_experimental_set( $context, array( 'typography', 'customFontSize' ), true );
+		gutenberg_experimental_set( $context, array( 'typography', 'lineHeight' ), true );
+		unset( $context['appearance'] );
+	}
+
 	/**
 	 * Sanitizes the input according to the schemas.
 	 *
diff --git a/lib/theme.json b/lib/theme.json
index 7629089219f8e..ecc8beceda717 100644
--- a/lib/theme.json
+++ b/lib/theme.json
@@ -1,6 +1,7 @@
 {
 	"version": 2,
 	"settings": {
+		"appearance": true,
 		"color": {
 			"background": true,
 			"palette": [
diff --git a/phpunit/class-wp-theme-json-test.php b/phpunit/class-wp-theme-json-test.php
index d8c9f47a14607..55036af9c107d 100644
--- a/phpunit/class-wp-theme-json-test.php
+++ b/phpunit/class-wp-theme-json-test.php
@@ -188,6 +188,75 @@ function test_get_settings_presets_are_keyed_by_origin() {
 		$this->assertEqualSetsWithIndex( $expected_no_origin, $actual_no_origin );
 	}
 
+	function test_get_settings_using_opt_in_key() {
+		$theme_json = new WP_Theme_JSON_Gutenberg(
+			array(
+				'version'  => WP_Theme_JSON_Gutenberg::LATEST_SCHEMA,
+				'settings' => array(
+					'appearance' => true,
+					'blocks'     => array(
+						'core/paragraph' => array(
+							'typography' => array(
+								'lineHeight' => false,
+							),
+						),
+						'core/group'     => array(
+							'appearance' => true,
+							'typography' => array(
+								'lineHeight' => false, // This is overridden by appearance.
+							),
+						),
+					),
+				),
+			)
+		);
+
+		$actual   = $theme_json->get_settings();
+		$expected = array(
+			'border'     => array(
+				'width'  => true,
+				'style'  => true,
+				'radius' => true,
+				'color'  => true,
+			),
+			'spacing'    => array(
+				'margin'  => true,
+				'padding' => true,
+				'units'   => true,
+			),
+			'typography' => array(
+				'customFontSize' => true,
+				'lineHeight'     => true,
+			),
+			'blocks'     => array(
+				'core/paragraph' => array(
+					'typography' => array(
+						'lineHeight' => false,
+					),
+				),
+				'core/group'     => array(
+					'border'     => array(
+						'width'  => true,
+						'style'  => true,
+						'radius' => true,
+						'color'  => true,
+					),
+					'spacing'    => array(
+						'margin'  => true,
+						'padding' => true,
+						'units'   => true,
+					),
+					'typography' => array(
+						'customFontSize' => true,
+						'lineHeight'     => true,
+					),
+				),
+			),
+		);
+
+		$this->assertEqualSetsWithIndex( $expected, $actual );
+	}
+
 	function test_get_stylesheet_support_for_shorthand_and_longhand_values() {
 		$theme_json = new WP_Theme_JSON_Gutenberg(
 			array(