Free browser tool
Make an MP4 ready for the web
Drop an MP4 in and get a WebM back, converted in this tab. Useful when a site, a wiki or a web app will only take WebM.
- No sign up
- Nothing uploaded
- No queue
- Up to 300 MB a file
Drop a MP4 in
Drag a file onto this panel or open one. It is converted to WebM in this tab, on your own machine, and never uploaded.
Only convert if something is asking for it
Every browser has played H.264 in an MP4 for years, so WebM is not a compatibility upgrade. It is what you produce when a particular place insists on a royalty-free codec: Wikipedia and Wikimedia Commons, some open-source project sites, and the occasional web app that validates uploads by codec.
If nothing is asking, keep the MP4.
VP8, and why not VP9
The video is encoded as VP8 at 1 Mbit with Vorbis audio. VP9 would make a smaller file and takes roughly four times as long to encode, which in a tab, on one thread, is the difference between waiting and closing it. Every browser that decodes VP9 also decodes VP8.
This is the slowest conversion on the site. A clip of a minute or two is the right size for it; anything longer belongs in ffmpeg or Handbrake on your machine.
The file will not necessarily shrink
At this bitrate a WebM usually lands close to the MP4 it came from, sometimes larger. Size is not the reason to do this. Compatibility with one specific destination is.
It runs in this tab
ffmpeg compiled to WebAssembly does the encoding on your own processor. The MP4 is never uploaded, which matters when it is an unreleased product video on its way to a public wiki.
How it works
Converting in 3 steps
- Drop the MP4 inAnything up to 300 MB. A short clip is the right shape for this one.
- ConvertThe video is encoded as VP8 and the audio as Vorbis, which is the pair every browser has decoded for a decade.
- DownloadThe WebM is ready to upload wherever the MP4 was refused.
What it does
Free, and still worth using
Satisfy a site that refuses MP4
Wikipedia, some forums and a number of open-source projects accept only royalty-free formats. WebM is what they mean, and this produces one without an account.
Convert a clip while you wait
VP8 at 1 Mbit is the setting here, chosen so a short clip finishes in about its own length rather than in four times it. VP9 would be smaller and far slower in a browser.
Keep the video off a server
The whole encode runs in this tab, so an unreleased product video is converted on your own machine rather than uploaded to somebody's queue.
Nothing to sign up for
No account, no email, no watermark and no cap on how many files you convert.
On a Mac, the editing is already done
Prequel records your screen at its full resolution, then opens an editor with the zooms already placed, your camera framed and a background applied. Export one MP4 at up to 4K.
No credit card required
- Zooms placed on every click
- Camera shaped, sized and framed
- Background, padding and shadow
- Microphone and system on separate gains
- Cursor smoothed and resized
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QuickTime in, MP4 out, rewrapped rather than re-encoded wherever it can be.
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A QuickTime recording in, its audio out as an MP3.
FAQ
Speed, quality and when to use WebM
Why is this conversion slower than the others?
Because every frame has to be encoded with VP8, and video encoding is the slowest thing a browser can be asked to do. It runs single-threaded in WebAssembly, so expect roughly the length of the clip, and keep to short ones.
Why VP8 rather than VP9?
VP9 makes smaller files and takes around four times as long to encode. In a tab, on one thread, that is the difference between waiting and giving up. VP8 plays in every browser that plays VP9.
Should I be converting to WebM at all?
Only if something is asking for it. Every browser has played H.264 MP4 for years, so WebM is for places with a royalty-free policy, such as Wikipedia, or for a specific web app that insists.
Does the file get smaller?
Not necessarily. At the bitrate used here a WebM is usually close to the MP4 it came from, and sometimes larger. Size is not the reason to convert; compatibility with a particular site is.
Is my video uploaded?
No. ffmpeg runs inside this tab and the MP4 never leaves your computer.
What is the size limit?
About 300 MB, and in practice you want far less for this conversion: it is the slowest of the set, so a clip of a minute or two is the right size.
What happens to the audio?
AAC is decoded and re-encoded as Vorbis, which is the audio codec WebM carries and every browser decodes.
Is there a version of this that does not need converting?
The browser recorder on this site writes WebM directly in Chrome and Firefox, so a recording made there needs no conversion at all.