The Media block embeds content from other sources, sometimes using an iframe, or a native media player in case it's a direct link to an mp3, wav, or mp4 file.

So in most cases, the accessibility of that content does not depend on us. 

However I guess we can improve the UX a bit on our side, suggestions: 

• In the case of the MP4 file, as the user can add an picture from the media library as cover image, add the caption in a visually-hidden div, so it can be read by the screen reader.

• For the rest of the cases, add an extra field to the Media Library block, added also as a visually-hidden element, to let editors describe the embedded content to visually impaired users.

The rest depends on the inserted element, the provider (Youtube, Vimeo, Soundcloud), or the browser in case of native controls (mp3, mp4, etc).

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