My HEVC videos upload to Synology Photos but will not play in the browser. How do I fix this?

Applies to: Synology Photos HEIC photos and HEVC/H.265 videos; not Surveillance Station camera decoding.

Work through these checks

1. Download one affected original and test it in a compatible local player. Keep it unchanged. Compare a JPEG or H.264 sample in Photos to separate a format problem from a general permission or connection failure.
2. Record DSM, Photos and browser versions, and whether files arrived through SMB, File Station, the web portal or the mobile app. Upload route affects preview generation on supported versions.
3. For supported desktop workflows, install the genuine Synology Image Assistant desktop app and matching browser extension. Both parts are required for the desktop toolkit. Check the operating system’s supported media-codec requirements.
4. Run the supported Image Assistant workflow or use its function in the current Photos mobile app. Allow processing to complete, then reopen the same sample in the web portal. Retain original-resolution files separately.

Confirm the result

The affected item displays and plays correctly in the intended browser, while downloading the original still returns the original file.

If you need help

Include these details in your ticket: DSM/Photos/browser versions, upload method, codec and whether the downloaded original plays locally.

Updated 261107