Index: src/wp-admin/includes/media.php
===================================================================
--- src/wp-admin/includes/media.php	(revision 52003)
+++ src/wp-admin/includes/media.php	(working copy)
@@ -3226,10 +3226,13 @@
 		<p class="attachment-alt-text-description" id="alt-text-description">
 		<?php
 
+		/* translators: Link to tutorial that describes how to use alternative text and alt attributes. */
+		$alt_text_tutorial = __( 'https://make.wordpress.org/accessibility/handbook/content/alternative-text-for-images/' );
+
 		printf(
 			/* translators: 1: Link to tutorial, 2: Additional link attributes, 3: Accessibility text. */
-			__( '<a href="%1$s" %2$s>Describe the purpose of the image%3$s</a>. Leave empty if the image is purely decorative.' ),
-			esc_url( 'https://www.w3.org/WAI/tutorials/images/decision-tree' ),
+			__( '<a href="%1$s" %2$s>Learn how to describe the purpose of the image%3$s</a>. Leave empty if the image is purely decorative.' ),
+			esc_url( $alt_text_tutorial ),
 			'target="_blank" rel="noopener"',
 			sprintf(
 				'<span class="screen-reader-text"> %s</span>',
Index: src/wp-includes/media-template.php
===================================================================
--- src/wp-includes/media-template.php	(revision 52003)
+++ src/wp-includes/media-template.php	(working copy)
@@ -156,10 +156,12 @@
 function wp_print_media_templates() {
 	$class = 'media-modal wp-core-ui';
 
+	/* translators: Link to tutorial that describes how to use alternative text and alt attributes. */
+	$alt_text_tutorial    = __( 'https://make.wordpress.org/accessibility/handbook/content/alternative-text-for-images/' );
 	$alt_text_description = sprintf(
 		/* translators: 1: Link to tutorial, 2: Additional link attributes, 3: Accessibility text. */
-		__( '<a href="%1$s" %2$s>Describe the purpose of the image%3$s</a>. Leave empty if the image is purely decorative.' ),
-		esc_url( 'https://www.w3.org/WAI/tutorials/images/decision-tree' ),
+		__( '<a href="%1$s" %2$s>Learn how to describe the purpose of the image%3$s</a>. Leave empty if the image is purely decorative.' ),
+		esc_url( $alt_text_tutorial ),
 		'target="_blank" rel="noopener"',
 		sprintf(
 			'<span class="screen-reader-text"> %s</span>',