Free tool
WebM to MP4 converter
Drop a WebM into this WebM to MP4 converter and it comes back as an MP4 with H.264 video and AAC sound, the pair that QuickTime Player, iMovie, iPhones and nearly every video editor open. It runs in your browser: a 30-second 720p clip took under 4 seconds.
- Free
- H.264 and AAC, the MP4 everyone plays
- Nothing is uploaded
Drop your WebM video here, or Choose your WebM video
MP4, MOV, WebM or MKV, up to 2 GB and 3 hours. Everything happens in your browser; nothing is uploaded.
How it works
How do you convert WebM to MP4?
Add the WebM and press Convert to MP4. The page decodes each frame with your browser’s VP9 or VP8 decoder and encodes it again as H.264, while the sound becomes AAC. A bar shows how far it has got, and the MP4 plays in the page when it’s done.
- 1
Add the WebM
A browser recording of your screen or camera, a clip saved from a website, a sticker or a download from a chat app.
- 2
Convert to MP4
Leave the tab open while it re-encodes; a short clip takes seconds, a long one a few minutes.
- 3
Download the MP4
Same name, same length, same picture size, now in the format your other apps expect.
Why won’t a WebM open on a Mac or iPhone?
WebM was made for web browsers. Chrome, Firefox, Edge and Safari play it, but QuickTime Player, iMovie and the iPhone’s Photos app don’t open it. The fix is the same video in an MP4 with H.264 and AAC, which they all read.
Browser recorders
Many screen and webcam recorders that run in a web page save WebM, the format browsers first recorded in.
Clips from websites
Many sites serve short videos and animations as WebM, so a saved clip often ends in .webm.
Chat and meeting apps
Some web apps hand you a WebM when you save a recording or an animated sticker.
Does converting WebM to MP4 lose quality?
A little, as any re-encode does, but not enough to see. The converter gives H.264 more data than the VP9 it replaces, because H.264 needs more for the same look, and keeps the picture size and frame rate as they were.
VP9 can sit in an MP4 file too, without re-encoding, but most apps that refuse WebM refuse VP9 as well, which is why the converter writes H.264.
How long does the conversion take?
A small part of the video’s length on a recent computer: our 30-second 720p VP9 clip took 3.1 seconds in Safari’s engine and 3.5 in Chrome’s, on a Mac with Apple silicon. A sharper or longer video takes longer, and a phone is slower.
Recording a meeting in the browser just to get notes?
There’s no need to convert anything. NoteOwl records the call on your Mac, from any app, with no bot joining, and gives you a transcript with speakers and a summary when it ends.
FAQ
Questions about converting WebM to MP4
Is my WebM uploaded?
No. The page reads the WebM from your device, re-encodes it with your browser’s own encoders and hands you the MP4. In our tests no network request left the page while it converted.
Can I keep the VP9 video and just change the container?
Not on this page, because the point of an MP4 is usually that it plays where WebM doesn’t, and those apps want H.264. If a WebM is only for another browser or web page, keep it as it is.
Why is the MP4 bigger than the WebM?
Because H.264 needs more data than VP9 for the same picture. The converter gives it enough to look the same, so the MP4 is usually somewhat larger. The video compressor can make it smaller afterwards.
What happens to a WebM with no sound?
You get an MP4 with no sound. Screen recordings made without a microphone and animated stickers are often silent, and the converter just leaves the sound track out.
Does it work in Safari?
Yes. Safari 26 decodes VP8 and VP9 and encodes H.264 and AAC, and it was the faster of the two browser engines we tested. Chrome and Edge work too.
Can I convert several WebM files at once?
One at a time. Convert the first, download it, then choose the next file; the converter is ready again as soon as each one finishes.
Keep exploring
More video tools
- MKV to MP4 converterRemux an MKV (an OBS recording, or a film with H.264 or HEVC) into an MP4 in your browser in seconds, without re-encoding
- MP4 to WebM converterConvert an MP4 to a VP9 and Opus WebM in your browser, for a web page’s video or anywhere WebM is asked for
- Video compressorMake a video smaller in your browser: pick a size to fit (10, 25 or 100 MB, or your own) or a quality, and see the size before and after
- Video trimmerTrim the start and end off a video in your browser with handles over its frames; copied without re-encoding, or cut on the exact frame
Related
- Online screen recorderRecord a screen, a window or a browser tab with your microphone and the tab’s sound, then download the video; computers only; nothing is uploaded
- WebM to MP3 converterConvert WebM to MP3 in your browser: the Opus or Vorbis sound of a browser or screen recording, saved as an MP3; nothing is uploaded
- Video to textTurn video to text free: drop in an MP4, MOV, M4V, MKV or WebM video and get an AI transcript with times, as text, SRT, VTT or Word; only the sound is sent, nothing is stored
Meeting notes without the recording chores
Free to download. Runs entirely on your Mac.
macOS 26 or later · Apple Silicon (M1 or newer) · 16 GB memory minimum, 24 GB recommended
About NoteOwl
NoteOwl is private AI meeting notes and memory for the Mac. It captures meetings without a bot joining the call, labels every speaker, writes summaries and action items, and builds a memory of every conversation that you can chat with — fully offline, because the speech recognition and the AI run on the Mac itself. Dictation into any app is free; Pro is a one-time purchase.
NoteOwl pricing: what’s free and what Pro adds
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