# `mix ffix.ffmpeg.checksum`
[🔗](https://github.com/akash-akya/ffix/blob/v0.2.0/lib/mix/tasks/ffix.ffmpeg.checksum.ex#L1)

Record checksums for a dated BtbN release before downloading a different build.

    mix ffix.ffmpeg.checksum --release autobuild-2026-09-07-15-39 --branch 9.0

Choose a dated tag from the [BtbN releases](https://github.com/BtbN/FFmpeg-Builds/releases).
`--release` is required; `--branch` defaults to `9.0`.

This updates `priv/ffmpeg/checksums.exs` with GPL and LGPL archive checksums for
supported platforms, preserving other branches. It downloads the checksum
listing only. Fetch the binaries afterward with `Mix.Tasks.Ffix.Ffmpeg.Fetch`.

Review and commit the manifest change when updating a project's pin. Checksums
verify downloaded bytes against the publisher's listing; they are not an
independent signature of the build.

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*Consult [api-reference.md](api-reference.md) for complete listing*