Index: src/wp-includes/customize/class-wp-customize-site-icon-control.php
===================================================================
--- src/wp-includes/customize/class-wp-customize-site-icon-control.php	(revision 37226)
+++ src/wp-includes/customize/class-wp-customize-site-icon-control.php	(working copy)
@@ -64,12 +64,12 @@
 			<div class="container">
 				<div class="site-icon-preview">
 					<div class="favicon-preview">
-						<img src="<?php echo esc_url( admin_url( 'images/browser.png' ) ); ?>" class="browser-preview" width="182" alt="<?php esc_attr_e( 'Browser interface preview' ); ?>" />
+						<img src="<?php echo esc_url( admin_url( 'images/browser.png' ) ); ?>" class="browser-preview" width="182" alt="" />
 
 						<div class="favicon">
 							<img id="preview-favicon" src="{{ data.attachment.sizes.full.url }}" alt="<?php esc_attr_e( 'Preview as a browser icon' ); ?>"/>
 						</div>
-						<span class="browser-title"><?php bloginfo( 'name' ); ?></span>
+						<span class="browser-title" aria-hidden="true"><?php bloginfo( 'name' ); ?></span>
 					</div>
 					<img class="app-icon-preview" src="{{ data.attachment.sizes.full.url }}" alt="<?php esc_attr_e( 'Preview as an app icon' ); ?>"/>
 				</div>
Index: src/wp-includes/media-template.php
===================================================================
--- src/wp-includes/media-template.php	(revision 37226)
+++ src/wp-includes/media-template.php	(working copy)
@@ -1232,13 +1232,13 @@
 	</script>
 
 	<script type="text/html" id="tmpl-crop-content">
-		<img class="crop-image" src="{{ data.url }}" alt="">
+		<img class="crop-image" src="{{ data.url }}" alt="<?php esc_attr_e( 'Image crop area preview. Requires mouse interaction.' ); ?>">
 		<div class="upload-errors"></div>
 	</script>
 
 	<script type="text/html" id="tmpl-site-icon-preview">
 		<h2><?php _e( 'Preview' ); ?></h2>
-		<strong><?php _e( 'As a browser icon' ); ?></strong>
+		<strong aria-hidden="true"><?php _e( 'As a browser icon' ); ?></strong>
 		<div class="favicon-preview">
 			<img src="images/browser.png" class="browser-preview" width="182" height="" alt="" />
 
@@ -1245,10 +1245,10 @@
 			<div class="favicon">
 				<img id="preview-favicon" src="{{ data.url }}" alt="<?php esc_attr_e( 'Preview as a browser icon' ); ?>"/>
 			</div>
-			<span class="browser-title"><?php bloginfo( 'name' ); ?></span>
+			<span class="browser-title" aria-hidden="true"><?php bloginfo( 'name' ); ?></span>
 		</div>
 
-		<strong><?php _e( 'As an app icon' ); ?></strong>
+		<strong aria-hidden="true"><?php _e( 'As an app icon' ); ?></strong>
 		<div class="app-icon-preview">
 			<img id="preview-app-icon" src="{{ data.url }}" alt="<?php esc_attr_e( 'Preview as an app icon' ); ?>"/>
 		</div>