# Optimize error: Unable to convert

**URL:** <https://forums.plex.tv/t/optimize-error-unable-to-convert/939232>\
**Category:** Plex Media Server\
**Tags:** server-linux\
**Created:** [May 28, 2026, 6:38pm UTC](https://forums.plex.tv/t/optimize-error-unable-to-convert/939232 "2026-05-28T18:38:24Z")\
**Posts on this page:** 1\
**Page:** 1

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**Author:** ![mcandre](https://sea1.discourse-cdn.com/plex/user_avatar/forums.plex.tv/mcandre/32/210047_2.png) [@mcandre](https://forums.plex.tv/u/mcandre)\
**Post date:** [May 28, 2026, 6:38pm UTC](https://forums.plex.tv/t/optimize-error-unable-to-convert/939232/1 "2026-05-28T18:38:24Z")

</div>

When I use the Plex optimize feature, then it often produces a generic error:

> Unable to convert

No further details are provided.

The original media are conventional MP4 files:

> <https://github.com/mcandre/reencode/blob/main/bin/reencode#L18-L22>

About 50% of the MP4 files successfully Plex optimize, with the remainder triggering that generic error above.