WebM to MP4 Converter
Runs in your browser — your files are never uploaded.
Turn a WebM clip (common from screen recordings and web video) into an MP4 that plays everywhere, including apps and devices with no WebM support. WebM’s VP8/VP9 video can’t be stored in an MP4 container as-is, so this tool re-encodes to H.264/AAC — using ffmpeg compiled to WebAssembly, running entirely on your device.
OptionsResolution: Original
How to convert WebM to MP4
- 1
Drop your WebM file onto the box, or click to choose one.
- 2
OkConverter re-encodes it to H.264 video / AAC audio locally.
- 3
Click “Download” to save the MP4.
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Frequently asked questions
Why would I convert WebM to MP4?+
WebM is a web-native format that some apps, editors and older devices — including much of the Apple ecosystem — won’t open. MP4 with H.264 plays virtually everywhere, so converting makes a clip you can share and edit without compatibility surprises.
How long will the conversion take?+
Because everything runs on your own device, it depends on the clip’s length, resolution and your computer’s speed. Short screen recordings finish quickly; long or high-resolution videos take proportionally longer, since each frame is re-encoded locally.
Why does this always re-encode instead of remuxing?+
WebM’s VP8/VP9 video and Vorbis/Opus audio codecs aren’t valid inside an MP4 container, so a fast remux isn’t possible here — a full re-encode to H.264/AAC is the normal path.
Is my video uploaded anywhere?+
No. The re-encode happens entirely inside your browser tab using WebAssembly ffmpeg — nothing is uploaded.