WebM to MP4, free.
Turn a screen recording, browser download or WebM clip into an MP4. Converted on your device, nothing uploaded.
How do I convert WebM to MP4 for free?
Drop the WebM into Cutmallow's free converter above and save the MP4. VP9 and AV1 video, which most WebM files use, is copied into the MP4 without re-encoding, so it takes seconds with no quality loss; older VP8 video is re-encoded to H.264. Opus sound is copied and Vorbis becomes AAC. It all runs in your browser: no upload, no watermark, no size limit.
Updated
- Output
- MP4
- VP9 / AV1
- Copied
- VP8
- To H.264
- Size limit
- None
How to use it
Drop a WebM (or tap to pick one).
Wait while it is copied or converted into an MP4.
Save the MP4. On a phone, the share sheet offers Save Video.
How it works
WebM is the open video format browsers and screen recorders write, with VP8, VP9 or AV1 video and Opus or Vorbis sound. An MP4 can carry VP9, AV1 and Opus as they are, so for most WebM files the converter copies the encoded packets into a new MP4 with no decoding at all: fast and lossless.
Older recordings use VP8 video, which an MP4 should not carry. Those frames are decoded and re-encoded to H.264 by your device’s hardware video encoder (WebCodecs), and Vorbis sound becomes AAC. The result screen says exactly what was copied and what was re-encoded.
It runs on Mediabunny, an open-source media library, in a background thread of the page. Your video never leaves your device.
Tips for a better result
- Screen recording from a browser? It is usually VP8 or VP9 WebM, and both convert here.
- If a site or app rejects the MP4, run it through the compressor with the H.264 format.
- For a GIF instead of a video, use the video to GIF tool with the same WebM.
Turn it into a Short
Cutmallow's free editor finishes the job. After converting, tap Edit in Cutmallow and your MP4 opens there, still on your device.
- Cuts the pauses and filler words
- Writes animated word-by-word captions
- Exports a 9:16 MP4 for Shorts, Reels and TikTok
Frequently asked questions
Something else? Write to hello@cutmallow.com.
Does converting WebM to MP4 lose quality?
Not for VP9 or AV1 video: it is copied exactly into the MP4. VP8 video is re-encoded to H.264 at a high bitrate, which looks the same to the eye but is technically a new encode. The result screen tells you which one happened.
Will the MP4 play on an iPhone?
An MP4 with H.264 video (from a VP8 WebM) plays everywhere. VP9 or AV1 video is copied as is, and older iPhones and some editors do not play it. In that case run the MP4 through the free video compressor with the H.264 format.
Can I convert WebM to MP4 on a phone?
Yes, in Chrome on Android or Safari on iPhone. Tap the drop box, pick the file from Files and save the MP4 from the share sheet. Copying VP9 needs no encoder, so it works on any current phone.
Is my video uploaded anywhere?
No. Your video never leaves your device. The file is opened and processed by your own browser, and the result is saved straight from your device.
Is there a file size or length limit?
No. The file is read from your device a piece at a time and the result is written to the browser’s private storage, so long and very large videos work. The only limit is free space on your device.