WebM to MP4 converter
Convert WebM to MP4 in your browser. Re-encodes VP8 or VP9 video to H.264 so the file plays outside a browser; the Opus audio becomes AAC along with it.
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Accepts .webm · Up to 20 files at a time · up to 667 MB each "Upload" and "download" here mean your browser reading a file from this device and writing one back to it. Nothing is sent to a server — open your browser's network panel and watch: no request carries your file.
FAQ
Why is my MP4 bigger than the WebM?
Because VP9 compresses more efficiently than H.264, particularly on screen recordings and animation. You are converting for compatibility, not for size, and giving up some of both is expected.
How long does it take?
A noticeable fraction of the clip's own duration, because every frame is decoded and re-encoded. A five-minute recording takes minutes rather than seconds. The estimate on the progress bar is based on your machine's measured rate.
Will quality drop?
Slightly. The video is compressed a second time, so some detail is lost. The default quality preset keeps this invisible for ordinary content; raise it if the recording contains fine text you need to stay crisp.
What happens to Opus audio?
It is re-encoded to AAC, because MP4 does not carry Opus in a form most players accept. As with the video, that is a second lossy pass on the audio.
Why does my editor refuse WebM?
Most editing software is built around the codecs that cameras produce, which means H.264 and HEVC. VP8 and VP9 came from the web rather than from the camera industry, so support outside browsers stayed patchy.
Is there a file size limit?
About 667 MB. Video conversions have to hold the incoming data, the outgoing file and the encoder's buffers at once, which puts the ceiling well below the one for extracting audio.
Is it really free?
Yes — every conversion on this site, with no account, no watermark and no daily cap. The work happens on your own device, so there is no server bill for us to pass on to you.
Do I need to install anything?
No. It runs in any modern browser, on Windows, macOS, Linux, Android and iOS. There is nothing to download and nothing to sign up for, and once the page has loaded it keeps working with the network switched off.
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