WP Accessibility adds a column to the media library list view to identify images with missing or inadequate alt
attributes. The tests include:
- Checking for common invalid values, such as
""
,''
, 
, empty spaces, or hyphens. - Identify images with no alternative text
- Identify images with unusually long alternate text. (Default check is 140 characters, but can be changed with a filter.)
- Identify images with suspicious alternate text. Suspicious alternate text values include the words ‘logo’, ‘image’, ‘picture’, ‘alt text’ or ‘alternative text’, or the strings ‘DSC’ or ‘IMG’ in all caps.
