diff --git a/docs/how-to-guides/themes/theme-json.md b/docs/how-to-guides/themes/theme-json.md
index 6c0b2392e22bbb..32f9bacacefc5e 100644
--- a/docs/how-to-guides/themes/theme-json.md
+++ b/docs/how-to-guides/themes/theme-json.md
@@ -91,7 +91,7 @@ To address this need, we've started to experiment with CSS Custom Properties, ak
 {% Output %}
 
 ```css
-:root {
+body {
 	--wp--preset--color--black: #000000;
 	--wp--preset--color--white: #ffffff;
 }
@@ -122,7 +122,7 @@ To address this need, we've started to experiment with CSS Custom Properties, ak
 {% Output %}
 
 ```css
-:root {
+body {
 	--wp--custom--line-height--body: 1.7;
 	--wp--custom--line-height--heading: 1.3;
 }
@@ -292,7 +292,7 @@ For example:
 {% Output %}
 
 ```css
-:root {
+body {
 	--wp--preset--color--strong-magenta: #a156b4;
 	--wp--preset--color--very-dark-gray: #444;
 	--wp--preset--font-size--big: 32;
@@ -344,7 +344,7 @@ For example:
 {% Output %}
 
 ```css
-:root {
+body {
 	--wp--custom--base-font: 16;
 	--wp--custom--line-height--small: 1.2;
 	--wp--custom--line-height--medium: 1.4;
@@ -434,7 +434,7 @@ For example:
 {% Output %}
 
 ```css
-:root {
+body {
 	color: var( --wp--preset--color--primary );
 }
 h1 {
@@ -549,7 +549,7 @@ For example:
 {% Output %}
 
 ```css
-:root {
+body {
 	--wp--custom--line-height--body: 1.7;
 	--wp--custom--font-primary: "-apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, Oxygen-Sans, Ubuntu, Cantarell, 'Helvetica Neue', sans-serif";
 }
diff --git a/lib/class-wp-theme-json.php b/lib/class-wp-theme-json.php
index 871cb9c1c68f5f..95447a0946358d 100644
--- a/lib/class-wp-theme-json.php
+++ b/lib/class-wp-theme-json.php
@@ -39,7 +39,7 @@ class WP_Theme_JSON {
 	 *
 	 * @var string
 	 */
-	const ALL_BLOCKS_SELECTOR = ':root';
+	const ALL_BLOCKS_SELECTOR = 'body';
 
 	/**
 	 * How to address the root block
@@ -54,7 +54,7 @@ class WP_Theme_JSON {
 	 *
 	 * @var string
 	 */
-	const ROOT_BLOCK_SELECTOR = ':root';
+	const ROOT_BLOCK_SELECTOR = 'body';
 
 	const VALID_TOP_LEVEL_KEYS = array(
 		'customTemplates',
@@ -356,7 +356,7 @@ private static function to_property( $css_name ) {
 	 *
 	 * {
 	 *   'root': {
-	 *     'selector': ':root'
+	 *     'selector': 'body'
 	 *   },
 	 *   'core/heading/h1': {
 	 *     'selector': 'h1'
diff --git a/packages/edit-site/src/components/editor/utils.js b/packages/edit-site/src/components/editor/utils.js
index b66725dbe647c5..b695c102ef1c60 100644
--- a/packages/edit-site/src/components/editor/utils.js
+++ b/packages/edit-site/src/components/editor/utils.js
@@ -13,9 +13,9 @@ import { store as editSiteStore } from '../../store';
 
 /* Supporting data */
 export const ALL_BLOCKS_NAME = 'defaults';
-export const ALL_BLOCKS_SELECTOR = ':root';
+export const ALL_BLOCKS_SELECTOR = 'body';
 export const ROOT_BLOCK_NAME = 'root';
-export const ROOT_BLOCK_SELECTOR = ':root';
+export const ROOT_BLOCK_SELECTOR = 'body';
 export const ROOT_BLOCK_SUPPORTS = [
 	'--wp--style--color--link',
 	'background',
diff --git a/phpunit/class-wp-theme-json-test.php b/phpunit/class-wp-theme-json-test.php
index 09ad612357c73a..372f6c7a7ba551 100644
--- a/phpunit/class-wp-theme-json-test.php
+++ b/phpunit/class-wp-theme-json-test.php
@@ -108,15 +108,15 @@ function test_get_stylesheet() {
 		);
 
 		$this->assertEquals(
-			':root{--wp--preset--color--grey: grey;--wp--preset--font-family--small: 14px;--wp--preset--font-family--big: 41px;}.wp-block-group{--wp--custom--base-font: 16;--wp--custom--line-height--small: 1.2;--wp--custom--line-height--medium: 1.4;--wp--custom--line-height--large: 1.8;}:root{--wp--style--color--link: #111;color: var(--wp--preset--color--grey);}.wp-block-group{padding-top: 12px;padding-bottom: 24px;}.has-grey-color{color: grey !important;}.has-grey-background-color{background-color: grey !important;}.has-grey-border-color{border-color: grey !important;}',
+			'body{--wp--preset--color--grey: grey;--wp--preset--font-family--small: 14px;--wp--preset--font-family--big: 41px;}.wp-block-group{--wp--custom--base-font: 16;--wp--custom--line-height--small: 1.2;--wp--custom--line-height--medium: 1.4;--wp--custom--line-height--large: 1.8;}body{--wp--style--color--link: #111;color: var(--wp--preset--color--grey);}.wp-block-group{padding-top: 12px;padding-bottom: 24px;}.has-grey-color{color: grey !important;}.has-grey-background-color{background-color: grey !important;}.has-grey-border-color{border-color: grey !important;}',
 			$theme_json->get_stylesheet()
 		);
 		$this->assertEquals(
-			':root{--wp--style--color--link: #111;color: var(--wp--preset--color--grey);}.wp-block-group{padding-top: 12px;padding-bottom: 24px;}.has-grey-color{color: grey !important;}.has-grey-background-color{background-color: grey !important;}.has-grey-border-color{border-color: grey !important;}',
+			'body{--wp--style--color--link: #111;color: var(--wp--preset--color--grey);}.wp-block-group{padding-top: 12px;padding-bottom: 24px;}.has-grey-color{color: grey !important;}.has-grey-background-color{background-color: grey !important;}.has-grey-border-color{border-color: grey !important;}',
 			$theme_json->get_stylesheet( 'block_styles' )
 		);
 		$this->assertEquals(
-			':root{--wp--preset--color--grey: grey;--wp--preset--font-family--small: 14px;--wp--preset--font-family--big: 41px;}.wp-block-group{--wp--custom--base-font: 16;--wp--custom--line-height--small: 1.2;--wp--custom--line-height--medium: 1.4;--wp--custom--line-height--large: 1.8;}',
+			'body{--wp--preset--color--grey: grey;--wp--preset--font-family--small: 14px;--wp--preset--font-family--big: 41px;}.wp-block-group{--wp--custom--base-font: 16;--wp--custom--line-height--small: 1.2;--wp--custom--line-height--medium: 1.4;--wp--custom--line-height--large: 1.8;}',
 			$theme_json->get_stylesheet( 'css_variables' )
 		);
 	}
@@ -187,7 +187,7 @@ public function test_get_stylesheet_preset_values_are_marked_as_important() {
 		);
 
 		$this->assertEquals(
-			':root{--wp--preset--color--grey: grey;}h2.wp-block-post-title{background-color: blue;color: red;font-size: 12px;line-height: 1.3;}.has-grey-color{color: grey !important;}.has-grey-background-color{background-color: grey !important;}.has-grey-border-color{border-color: grey !important;}',
+			'body{--wp--preset--color--grey: grey;}h2.wp-block-post-title{background-color: blue;color: red;font-size: 12px;line-height: 1.3;}.has-grey-color{color: grey !important;}.has-grey-background-color{background-color: grey !important;}.has-grey-border-color{border-color: grey !important;}',
 			$theme_json->get_stylesheet()
 		);
 	}