Is there a size limit for WebM files?

There's no fixed limit, but because your own device does the encoding, very large files use a lot of memory and time. Short clips convert fastest.

Yes — the audio track is carried into the MP4 (re-encoded to AAC when a re-encode is needed).

Convert WebM to MP4

Convert WebM videos to MP4 (H.264) for editors and apps that reject WebM. Converted entirely in your browser — nothing is uploaded.

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Why convert WebM to MP4?

MP4 is the most widely supported video format there is. Converting from WebM fixes "unsupported file" errors on phones, social uploads, presentation software, and video editors.

How the conversion works

The WebM is decoded and re-encoded to H.264 video with AAC audio, the combination that plays on virtually every phone, browser, TV, and editor.

Encoding happens on your device

Video encoding happens entirely in your browser using WebAssembly. There is no upload and no queue, but that also means your device does the work — expect a large or long clip to take a minute or more.

How to webm to mp4

Drop your WebM file into the zone above.
Press Convert. Everything runs locally in your browser.
Download the MP4 when it's ready.

Related converters

Compress VideoShrink MP4 file size with a quality slider and resolution cap.MP4 to WebMTurn MP4 videos into open, web-friendly WebM (VP9/Opus).Trim VideoCut a clip to a start and end time without re-encoding.