diff --git src/wp-includes/js/media-editor.js src/wp-includes/js/media-editor.js
index 5bf5bd3..870439c 100644
--- src/wp-includes/js/media-editor.js
+++ src/wp-includes/js/media-editor.js
@@ -55,7 +55,14 @@
 			fallbacks = function( props ) {
 				// Generate alt fallbacks and strip tags.
 				if ( 'image' === props.type && ! props.alt ) {
-					props.alt = props.caption || props.title || '';
+					if ( props.caption ) {
+						props.alt = props.caption;
+					} else if ( props.title !== props.url ) {
+						props.alt = props.title;
+					} else {
+						props.alt = '';
+					}
+
 					props.alt = props.alt.replace( /<\/?[^>]+>/g, '' );
 					props.alt = props.alt.replace( /[\r\n]+/g, ' ' );
 				}
@@ -894,7 +901,8 @@
 						title:   embed.url,
 						linkUrl: '',
 						align:   'none',
-						link:    'none'
+						link:    'none',
+						type:    'image'
 					});
 
 					if ( 'none' === embed.link ) {