Synology NAS Photos Thumbnail Not Generated: How to Fix It

Easy 15 minutes to 4+ hours depending on library size Low Severity Verified June 2026
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Error Code
Photos thumbnail not generated
Brand
Synology
Product Type
nas
Severity
Low
DIY Difficulty
Easy
Estimated Fix Time
15 minutes to 4+ hours depending on library size
When Synology Photos shows 'thumbnail not generated' or thumbnails fail to load, it usually means the system is still processing your photo library for the first time. This is a normal indexing process that can take several hours to complete depending on your library size.
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Tools You'll Need

How to Fix Error Code Photos thumbnail not generated

  1. Check indexing status

  2. Verify sufficient storage space

  3. Restart Synology Photos service

  4. Clear Photos cache

    Back up your Photos database before clearing cache files to avoid potential data loss.

  5. Rebuild photo database

    Re-indexing will reset all album organization and facial recognition data.

  6. Check file permissions

  7. Update DSM and Photos app

    Create a system backup before updating DSM to avoid potential data loss.
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When to Call a Professional

Contact Synology support if thumbnails still don't generate after 24+ hours of indexing, if you get database corruption errors, or if the NAS becomes unresponsive during the process. Professional help may be needed for hardware issues like failing storage drives.

Frequently Asked Questions

How long does Synology Photos thumbnail generation take?
Thumbnail generation time depends on your library size and NAS model. Small libraries (under 1000 photos) may take 1-2 hours, while large libraries (50,000+ photos) can take 12-24 hours or more. Higher-end NAS models with faster processors complete the task quicker.
Why are some thumbnails missing while others show up?
This is normal during the initial indexing process. Synology Photos generates thumbnails in batches, so you'll see partial results while processing continues. Unsupported file formats or corrupted files may permanently fail to generate thumbnails.
Can I speed up Synology Photos thumbnail generation?
Yes, temporarily disable other resource-intensive tasks like Cloud Sync or backup jobs. Close unnecessary DSM applications and avoid heavy file transfers during indexing. Ensure your NAS has adequate RAM and consider upgrading if you frequently work with large photo libraries.
What file formats does Synology Photos support for thumbnails?
Synology Photos supports JPEG, PNG, TIFF, BMP, GIF, HEIC, and RAW formats from major camera manufacturers. Video thumbnails work with MP4, MOV, AVI, and other common formats. Unsupported or corrupted files won't generate thumbnails.
Will re-indexing delete my photos?
No, re-indexing only rebuilds the database and thumbnails - your original photos remain untouched. However, you'll lose custom albums, face recognition data, and other organizational metadata. Manual albums and favorites will need to be recreated.

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