rendercheck

The worst bugs in generated media don’t throw. Drop a file and watch these ones throw.

The same checks as the command-line tool, running on a build of ffmpeg compiled to WebAssembly.

Drop an audio or video file
or click to choose · mp3, wav, m4a, mp4, mov, webm

● Nothing is uploaded. The file is decoded in this tab and never leaves your machine — there is no server to send it to.

What it measures

Loudness in LUFS, silent stretches, samples clipped at full scale, whether the audio was allowed to finish, and — for video — black and frozen stretches. Same thresholds as the CLI.

Why the browser is slower

WebAssembly decodes at a fraction of native speed and this page downloads ~32 MB of ffmpeg the first time. Short clips are pleasant; a 40-minute lesson is not. Use the CLI for those.

Run it properly

pip install rendercheck then rendercheck demo. It takes directories, has a --json mode, and exits non-zero when a render is broken — or when nothing could be measured.