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Duplicate detection

docs/docs/photos/features/backup-and-sync/duplicate-detection.md

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Duplicate detection

Ente automatically detects and handles duplicate files during backup to save storage space and upload time. This happens transparently in the background without any action required from you.

How automatic detection works

When uploading photos and videos, Ente uses a hash-based system to identify duplicate files:

Same file to same album:

  • If you try to upload an exact duplicate to an album where it already exists, Ente will skip it entirely
  • This allows you to safely resume interrupted uploads or re-upload folders without creating duplicates

Same file to different albums:

  • If the same file already exists in a different album, Ente creates a symlink (reference) instead of storing it again
  • The file appears in both albums, but storage is only counted once
  • This is the same behavior as using "Add to album" within Ente

Platform-specific behavior

The duplicate detection works slightly differently on each platform to match platform conventions:

Mobile (iOS and Android)

  • Uses hash-based detection for exact duplicates
  • If uploading to the same album: duplicate is skipped
  • If uploading to a different album: creates a symlink (no data uploaded)
  • Storage is only counted once regardless of how many albums contain the photo

Web and desktop

On laptops using the web or desktop app, both the file hash AND filename are used for detection:

  • A file is considered duplicate if it has the same name AND same hash
  • This assumes users want to keep two copies if they have the same file but with different names
  • If uploading to the same album: exact duplicate (same name + hash) is skipped
  • If uploading to a different album: symlink is created (similar to "Add to album")

Benefits

Saves storage space:

  • Each unique file is only stored once, even if it appears in multiple albums
  • Symlinks count minimal storage compared to full copies

Saves upload time:

  • Duplicate files are detected immediately and skipped
  • Only new or modified files need to be uploaded

Enables safe re-uploads:

  • You can safely drag and drop the same folder multiple times
  • Resume interrupted uploads without worrying about duplicates
  • Reinstall the app and re-configure backups without creating duplicates

Adding files to albums within Ente

Once a file is backed up to Ente, adding it to another Ente album always creates a symlink. This means:

  • You can add photos to as many albums as you want
  • Storage is only counted once
  • Changes or deletions affect the file across all albums

For manual cleanup of existing duplicates, see Storage optimization.