MP4 to WebM, free.
Make an open-format WebM for your website, an HTML5 player or a web app. Encoded on your device, nothing uploaded.
How do I convert MP4 to WebM for free?
Drop the MP4 into Cutmallow's free converter above and save the WebM. H.264 or HEVC video (what most MP4s hold) is encoded to VP9 and AAC sound to Opus at 192 kbps, the codecs every browser plays in a WebM. If the MP4 already holds VP9 or AV1, it is copied without re-encoding. Everything runs in your browser: no upload, no watermark, no size limit.
Updated
- Output
- WebM
- Video
- VP9
- Sound
- Opus
- Size limit
- None
How to use it
Drop an MP4 (or tap to pick one).
Wait while the video is encoded to VP9 and the sound to Opus.
Save the WebM.
How it works
WebM is the open, royalty-free video format made for the web: VP8, VP9 or AV1 video with Opus or Vorbis sound. Websites use it in HTML5 video tags, where it often comes out smaller than H.264 at the same quality.
An MP4 usually holds H.264 video, which a WebM cannot carry, so the converter decodes each frame and encodes it to VP9 with your browser’s own encoder (WebCodecs), and turns AAC sound into Opus. When the MP4 already holds VP9 or AV1, those packets are copied straight across, which takes seconds and changes nothing.
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
- For a website, serve the WebM with the MP4 as a fallback for older Apple devices.
- Going the other way? Use the WebM to MP4 converter.
- For a looping animation, a WebM or MP4 is far smaller than a GIF.
Turn it into a Short
Cutmallow's free editor finishes the job. After converting, tap Edit in Cutmallow to keep working on the video, 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.
Is WebM better than MP4?
For websites, often: VP9 in a WebM is usually smaller than H.264 at the same quality and plays in every current browser. For phones, editors and social apps, MP4 with H.264 is still the safest choice.
Does converting to WebM lose quality?
Encoding H.264 to VP9 is a new encode at a high bitrate, which looks the same to the eye but is technically not identical. VP9 or AV1 video that is already in the MP4 is copied exactly.
Why is it slower than the WebM to MP4 converter?
That direction usually copies the video, which takes seconds. This one has to encode every frame to VP9, which is more work for your device.
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.