TamizhApps Unused Media Cleaner scans your Media Library in small batches and checks where every file is used. It then marks each file as Used, Unused or Needs review.
Where it looks
Files are matched by full URL, file name and every resized version (for example photo-300x200.jpg), as well as by attachment ID.
Safe cleanup
For new and existing sites
Important: always take a full backup before cleaning up. No automatic tool can detect every use. Images loaded only from CSS backgrounds, custom JavaScript, external sites or emails may not be detected.