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 "", '', &nbsp, 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.
Shows the variations on how different alt status is shown in the media library.
Some alt text labelling variations