diff --git a/includes/amp-helper-functions.php b/includes/amp-helper-functions.php
index 8f38a404933..a57829efd48 100644
--- a/includes/amp-helper-functions.php
+++ b/includes/amp-helper-functions.php
@@ -1462,7 +1462,7 @@ function amp_is_native_img_used() {
 	 *
 	 * @param bool $use_native Whether to use `img`.
 	 */
-	return (bool) apply_filters( 'amp_native_img_used', false );
+	return (bool) apply_filters( 'amp_native_img_used', true );
 }
 
 /**
diff --git a/includes/sanitizers/class-amp-img-sanitizer.php b/includes/sanitizers/class-amp-img-sanitizer.php
index efd641b75a6..7d36819f4c0 100644
--- a/includes/sanitizers/class-amp-img-sanitizer.php
+++ b/includes/sanitizers/class-amp-img-sanitizer.php
@@ -54,7 +54,7 @@ class AMP_Img_Sanitizer extends AMP_Base_Sanitizer {
 	 */
 	protected $DEFAULT_ARGS = [
 		'add_noscript_fallback' => true,
-		'native_img_used'       => false,
+		'native_img_used'       => true,
 	];
 
 	/**
diff --git a/includes/sanitizers/class-amp-style-sanitizer.php b/includes/sanitizers/class-amp-style-sanitizer.php
index 4135cab6d0d..8cd819126ae 100644
--- a/includes/sanitizers/class-amp-style-sanitizer.php
+++ b/includes/sanitizers/class-amp-style-sanitizer.php
@@ -155,6 +155,7 @@ class AMP_Style_Sanitizer extends AMP_Base_Sanitizer {
 	protected $DEFAULT_ARGS = [
 		'disable_style_processing'       => false,
 		'dynamic_element_selectors'      => [
+			'amp-img',
 			'amp-list',
 			'amp-live-list',
 			'[submit-error]',
diff --git a/tests/php/test-amp-helper-functions.php b/tests/php/test-amp-helper-functions.php
index b70d0881046..1709b07a6cf 100644
--- a/tests/php/test-amp-helper-functions.php
+++ b/tests/php/test-amp-helper-functions.php
@@ -1790,13 +1790,13 @@ public function test_amp_is_dev_mode() {
 	 * @covers ::amp_is_native_img_used()
 	 */
 	public function test_amp_is_native_img_used() {
-		$this->assertFalse( amp_is_native_img_used(), 'Expected to be disabled by default for now.' );
+		$this->assertTrue( amp_is_native_img_used(), 'Expected to be disabled by default for now.' );
 
-		add_filter( 'amp_native_img_used', '__return_true' );
-		$this->assertTrue( amp_is_native_img_used() );
-
-		add_filter( 'amp_native_img_used', '__return_false', 20 );
+		add_filter( 'amp_native_img_used', '__return_false' );
 		$this->assertFalse( amp_is_native_img_used() );
+
+		add_filter( 'amp_native_img_used', '__return_true', 20 );
+		$this->assertTrue( amp_is_native_img_used() );
 	}
 
 	/**
diff --git a/tests/php/test-amp-img-sanitizer.php b/tests/php/test-amp-img-sanitizer.php
index f77535ab80d..df5d652c1de 100644
--- a/tests/php/test-amp-img-sanitizer.php
+++ b/tests/php/test-amp-img-sanitizer.php
@@ -45,7 +45,7 @@ public function test_get_selector_conversion_mapping() {
 
 		$with_defaults = new AMP_Img_Sanitizer( $dom );
 		$this->assertEquals(
-			[ 'img' => [ 'amp-img', 'amp-anim' ] ],
+			[],
 			$with_defaults->get_selector_conversion_mapping()
 		);
 
@@ -521,6 +521,11 @@ public function test_converter( $source, $expected = null, $args = [], $expected
 
 		$error_codes = [];
 
+		$args = array_merge(
+			[ 'native_img_used' => false ],
+			$args
+		);
+
 		$args = array_merge(
 			[
 				'use_document_element'      => true,
@@ -584,7 +589,7 @@ public function test_no_gif_image_scripts() {
 		$expected = [ 'amp-anim' => true ];
 
 		$dom       = AMP_DOM_Utils::get_dom_from_content( $source );
-		$sanitizer = new AMP_Img_Sanitizer( $dom );
+		$sanitizer = new AMP_Img_Sanitizer( $dom, [ 'native_img_used' => false ] );
 		$sanitizer->sanitize();
 
 		$validating_sanitizer = new AMP_Tag_And_Attribute_Sanitizer( $dom );
@@ -609,7 +614,7 @@ public function test_image_block_link_to_media_file_with_lightbox() {
 		$expected = '<figure class="wp-block-image" data-amp-lightbox="true"><amp-img src="https://placehold.it/100x100" width="100" height="100" data-foo="bar" role="button" tabindex="0" data-amp-lightbox="" lightbox="" class="amp-wp-enforced-sizes" layout="intrinsic"><noscript><img src="https://placehold.it/100x100" width="100" height="100" role="button" tabindex="0"></noscript></amp-img></figure>';
 
 		$dom       = AMP_DOM_Utils::get_dom_from_content( $source );
-		$sanitizer = new AMP_Img_Sanitizer( $dom );
+		$sanitizer = new AMP_Img_Sanitizer( $dom, [ 'native_img_used' => false ] );
 		$sanitizer->sanitize();
 
 		$sanitizer = new AMP_Tag_And_Attribute_Sanitizer( $dom );
@@ -630,7 +635,7 @@ public function test_image_block_link_to_media_file_and_alignment_with_lightbox(
 		$expected = '<div data-amp-lightbox="true" class="wp-block-image"><figure class="alignright size-large"><amp-img src="https://placehold.it/100x100" width="100" height="100" data-foo="bar" role="button" tabindex="0" data-amp-lightbox="" lightbox="" class="amp-wp-enforced-sizes" layout="intrinsic"><noscript><img src="https://placehold.it/100x100" width="100" height="100" role="button" tabindex="0"></noscript></amp-img></figure></div>';
 
 		$dom       = AMP_DOM_Utils::get_dom_from_content( $source );
-		$sanitizer = new AMP_Img_Sanitizer( $dom );
+		$sanitizer = new AMP_Img_Sanitizer( $dom, [ 'native_img_used' => false ] );
 		$sanitizer->sanitize();
 
 		$sanitizer = new AMP_Tag_And_Attribute_Sanitizer( $dom );
diff --git a/tests/php/test-amp-style-sanitizer.php b/tests/php/test-amp-style-sanitizer.php
index bed80db0232..da07c12ba1e 100644
--- a/tests/php/test-amp-style-sanitizer.php
+++ b/tests/php/test-amp-style-sanitizer.php
@@ -1298,6 +1298,9 @@ public function get_amp_selector_data() {
 				sprintf( '<div><img class="logo" src="%s" width="200" height="100"></div>', admin_url( 'images/wordpress-logo.png' ) ),
 				'div img.logo{border:solid 1px red}',
 				'div amp-img.logo{border:solid 1px red}', // Note amp-anim is still tree-shaken because it doesn't occur in the DOM.
+				[
+					AMP_Img_Sanitizer::class => [ 'native_img_used' => false ],
+				],
 			],
 			'img-missing-class' => [
 				sprintf( '<div><img class="logo" src="%s" width="200" height="100"></div>', admin_url( 'images/wordpress-logo.png' ) ),
@@ -1308,16 +1311,25 @@ public function get_amp_selector_data() {
 				sprintf( '<div><img class="logo" src="%s" width="200" height="100"><img class="spinner" src="%s" width="200" height="100"></div>', admin_url( 'images/wordpress-logo.png' ), admin_url( 'images/spinner-2x.gif' ) ),
 				'div img{border:solid 1px red}',
 				'div amp-img,div amp-anim{border:solid 1px red}',
+				[
+					AMP_Img_Sanitizer::class => [ 'native_img_used' => false ],
+				],
 			],
 			'amp-img-and-amp-anim' => [
 				sprintf( '<amp-img class="logo amp-wp-enforced-sizes" src="%s" width="200" height="100" layout="intrinsic"></amp-img><amp-anim class="spinner amp-wp-enforced-sizes" src="%s" width="200" height="100" layout="intrinsic"></amp-anim>', admin_url( 'images/wordpress-logo.png' ), admin_url( 'images/spinner-2x.gif' ) ),
 				'amp-img.amp-wp-enforced-sizes[layout="intrinsic"] > img,amp-anim.amp-wp-enforced-sizes[layout="intrinsic"] > img{object-fit:contain}',
 				'amp-img.amp-wp-enforced-sizes[layout="intrinsic"] > img,amp-anim.amp-wp-enforced-sizes[layout="intrinsic"] > img{object-fit:contain}',
+				[
+					AMP_Img_Sanitizer::class => [ 'native_img_used' => false ],
+				],
 			],
 			'admin-bar-style-selectors' => [
 				'<div id="wpadminbar"><a href="https://example.com/"><amp-img src="https://example.com/foo.png" width="100" height="100"></amp-img><amp-anim src="https://example.com/foo.gif" width="100" height="100"></amp-anim></a></div>',
 				'#wpadminbar a, #wpadminbar a:hover, #wpadminbar a img, #wpadminbar a img:hover { border: none; text-decoration: none; background: none;}',
 				'#wpadminbar a,#wpadminbar a:hover,#wpadminbar a amp-img,#wpadminbar a amp-anim,#wpadminbar a amp-img:hover,#wpadminbar a amp-anim:hover{border:none;text-decoration:none;background:none}',
+				[
+					AMP_Img_Sanitizer::class => [ 'native_img_used' => false ],
+				],
 			],
 			'img_with_amp_img' => [
 				'<amp-img></amp-img>',
@@ -1328,6 +1340,9 @@ public function get_amp_selector_data() {
 				sprintf( '<div><amp-img class="logo" src="%s" width="200" height="100"></amp-img></div>', admin_url( 'images/wordpress-logo.png' ) ),
 				'div amp-img.logo img{object-fit:cover}',
 				'div amp-img.logo img{object-fit:cover}',
+				[
+					AMP_Img_Sanitizer::class => [ 'native_img_used' => false ],
+				],
 			],
 			'img-tree-shaking' => [
 				sprintf( '<article><img class="logo" src="%s" width="200" height="100"></article>', admin_url( 'images/wordpress-logo.png' ) ),
@@ -1649,6 +1664,8 @@ static function ( $selector ) {
 			)
 		);
 
+		add_filter( 'amp_native_img_used', '__return_false' );
+
 		// The toggling of the 'add_noscript_fallback' arg is to catch a bizzare PHP DOM issue whereby if you replace
 		// an element in a Document, and that replaced element had an ID, the element will still be returned by
 		// getElementById even though it is no longer inside of the document. When add_noscript_fallback is false,
@@ -3392,7 +3409,9 @@ function() {
 							?>
 							<figure class="wp-block-audio"><figcaption></figcaption></figure>
 							<div class="wp-block-foo"><figcaption></figcaption></div>
-							<img src="https://example.com/example.jpg" width="100" height="200">
+							<div class="amp-wp-default-form-message">
+								<p>Hi</p>
+							</div>
 							<?php
 						}
 					);
@@ -3415,7 +3434,7 @@ function( $original_dom, $original_source, $amphtml_dom, $amphtml_source ) {
 
 					$this->assertStringContainsString( '.wp-block-audio figcaption', $amphtml_source, 'Expected block-library/style.css' );
 					$this->assertStringContainsString( '[class^="wp-block-"]:not(.wp-block-gallery) figcaption', $amphtml_source, 'Expected twentyten/blocks.css' );
-					$this->assertStringContainsString( 'amp-img img', $amphtml_source, 'Expected amp-default.css' );
+					$this->assertStringContainsString( '.amp-wp-default-form-message>p', $amphtml_source, 'Expected amp-default.css' );
 					$this->assertStringContainsString( 'ab-empty-item', $amphtml_source, 'Expected admin-bar.css to still be present.' );
 					$this->assertStringNotContainsString( 'earlyprintstyle', $amphtml_source, 'Expected early print style to not be present.' );
 					$this->assertStringContainsString( 'admin-bar', $amphtml_dom->body->getAttribute( 'class' ) );
diff --git a/tests/php/test-class-amp-theme-support.php b/tests/php/test-class-amp-theme-support.php
index f6e819fd0cc..3b21bb52620 100644
--- a/tests/php/test-class-amp-theme-support.php
+++ b/tests/php/test-class-amp-theme-support.php
@@ -1614,7 +1614,7 @@ public function test_finish_output_buffering() {
 		$this->assertTrue( AMP_Theme_Support::is_output_buffering() );
 		$this->assertSame( 3, ob_get_level() );
 
-		echo '<html><head></head><body><img src="test.png"><script data-test>document.write(\'Illegal\');</script>';
+		echo '<html><head></head><body><video src="test.mp4" width="100" height="100"></video><script data-test>document.write(\'Illegal\');</script>';
 		wp_footer();
 
 		// Additional nested output bufferings which aren't getting closed.
@@ -1638,7 +1638,7 @@ static function( $response ) {
 		$this->assertStringContainsString( '<html amp', $output );
 		$this->assertStringContainsString( 'foo', $output );
 		$this->assertStringContainsString( 'BAR', $output );
-		$this->assertStringContainsString( '<amp-img src="test.png"', $output );
+		$this->assertStringContainsString( '<amp-video src="test.mp4"', $output );
 		$this->assertStringNotContainsString( '<script data-test', $output );
 
 	}
@@ -1655,11 +1655,11 @@ public function test_filter_customize_partial_render() {
 		AMP_Theme_Support::init();
 		AMP_Theme_Support::finish_init();
 
-		$partial = '<img src="test.png" style="border:solid 1px red;"><script data-head>document.write(\'Illegal\');</script><style>img { background:blue }</style>';
+		$partial = '<video src="test.mp4" width="100" height="200" style="border:solid 1px red;"></video><script data-head>document.write(\'Illegal\');</script><style>video { background:blue }</style>';
 		$output  = AMP_Theme_Support::filter_customize_partial_render( $partial );
-		$this->assertStringContainsString( '<amp-img src="test.png"', $output );
+		$this->assertStringContainsString( '<amp-video src="test.mp4"', $output );
 		$this->assertStringContainsString( '<style amp-custom-partial="">', $output );
-		$this->assertStringContainsString( 'amp-img{background:blue}', $output );
+		$this->assertStringContainsString( 'amp-video{background:blue}', $output );
 		$this->assertStringContainsString( ':root:not(#_):not(#_):not(#_):not(#_):not(#_) .amp-wp-b123f72{border:solid 1px red}', $output );
 		$this->assertStringEndsWith( '/*# sourceURL=amp-custom-partial.css */</style>', $output );
 		$this->assertStringNotContainsString( '<script', $output );
@@ -1770,8 +1770,9 @@ function ( $dom, $effective_sandboxing_level ) {
 			$prev_ordered_contain = $ordered_contain;
 		}
 
-		$this->assertStringContainsString( '<noscript><img', $sanitized_html );
-		$this->assertStringContainsString( '<amp-img', $sanitized_html );
+		$this->assertStringNotContainsString( '<noscript><img', $sanitized_html );
+		$this->assertStringContainsString( '<img width="100" height="100" src="https://example.com/hero.png" decoding="async" class="amp-wp-enforced-sizes">', $sanitized_html );
+		$this->assertStringContainsString( '<img width="100" height="100" src="https://example.com/test.png" loading="lazy" decoding="async" class="amp-wp-enforced-sizes">', $sanitized_html );
 
 		$this->assertStringContainsString( '<noscript><audio', $sanitized_html );
 		$this->assertStringContainsString( '<amp-audio', $sanitized_html );
@@ -2163,9 +2164,8 @@ static function() {
 		</head>
 		<body><!-- </body></html> -->
 		<div id="dynamic-id-0"></div>
-		<!-- 2nd image is needed for testing <noscript> as first is SSR'ed -->
 		<img width="100" height="100" src="https://example.com/hero.png">
-		<img width="100" height="100" src="https://example.com/test.png">
+		<img width="100" height="100" src="https://example.com/test.png" loading="lazy">
 		<audio src="https://example.com/audios/myaudio.mp3"></audio>
 		<amp-ad type="a9"
 				width="300"