Convert
Make screen recordings shareable as MP4
Convert WebM files (browser screen recordings, exported clips) into widely supported MP4s, locally.
For the best results: Browser screen recordings convert cleanly; if yours was recorded without audio the MP4 will simply have no sound track. Convert before importing into editors like Premiere that refuse WebM.
Advanced settingsoptional, defaults work well
Converted entirely in your browser, your files are never uploaded. Very large files depend on your device's memory.
What is WebM to MP4?
WebM to MP4 is a free file converter that converts WebM files (the format browsers produce for screen recordings) into MP4s that video editors and messaging apps accept. The video is processed by an ffmpeg engine running inside your browser, so your footage is never uploaded anywhere. There is no queue and no watermark, and after the first load it keeps working without a connection.
- ✦Runs entirely in your browser. Nothing you enter is ever uploaded
- ✦No account, no sign-up, and no data leaves your device
- ✦Works offline once the page has loaded
See it in action
A browser screen recording (always WebM) has to be uploaded to a portal that only accepts MP4.
What you drop in
screen.webm
What you get
screen.mp4 at identical dimensions and duration, verified 320x240 and 2.0 seconds in the test run, encoded H.264 for universal playback.
Tip: Screen recordings are mostly static pixels, so they compress beautifully: expect the MP4 to be similar in size or smaller. The +faststart flag is set for you, meaning the file starts playing before it fully downloads.
Use cases
What people use it for
Convert a browser screen recording of a bug into an MP4 the ticketing system will attach.
Turn WebM output from an online recording tool into a file Premiere Pro imports without complaint.
Make a screen-captured product demo sendable through workplace messaging apps that reject WebM.
Who uses WebM to MP4?
Software testers
convert browser-captured bug reproductions into MP4s that attach to tickets and play for any developer
Remote team leads
turn recorded browser meetings into files that archive properly and open on every colleague's machine
Product marketers
transform web-app demo captures into MP4s ready for editing suites and social scheduling tools
How it works
- 1Choose your files. They open in your browser, not on a server.
- 2Your device converts, compresses, or resizes them locally, with no upload.
- 3The converted files download straight back; nothing is kept anywhere.
Tips for the best results
- Convert bug recordings before attaching them, since ticket systems preview MP4 far more reliably.
- A recording with odd seeking behavior will usually scrub properly once rebuilt as MP4.
- Long meeting captures convert best on a plugged-in computer with the tab left in front.
- Keep recordings of sensitive screens local by converting here instead of through an upload site.
- Trim the recording first if only a section matters, so the re-encode has less to chew through.
FAQ
Frequently asked questions
What is a WebM file and why do I keep getting them?
WebM is an open, royalty-free container built for the web, carrying video as VP8 or VP9 and audio as Vorbis or Opus. Browsers adore it, which is why screen recorders built into Chrome, Firefox, and countless web apps produce it by default. The trouble starts the moment the file leaves the browser world it was designed for.
Why do editing programs and apps reject WebM?
Support outside browsers has always trailed. Many editing suites, messaging platforms, and phones either skipped VP8 and VP9 decoders or added them late and partially, since their pipelines were built around the MPEG family of codecs. MP4 with H.264 is the format those tools were engineered to expect, so conversion removes the friction at the source.
What does the conversion do to my recording?
It decodes the VP8 or VP9 video and re-encodes it as H.264, converts the audio to AAC, and wraps both in an MP4 container. Screen recordings, being mostly static with bursts of change, generally re-encode cleanly, with text staying crisp. The result is a file that behaves in editors, email, and chat the way people expect video to.
Does my screen recording get uploaded to convert it?
No. A screen recording is often the most sensitive file on your machine, full of visible emails, names, and internal tools, and that is precisely why this conversion runs locally. The ffmpeg engine executes as WebAssembly in the tab, and everything on that screen stays in your browser's memory until you download the finished MP4 yourself.
How long does converting a WebM take?
It scales with length and resolution, since every frame is genuinely re-encoded on your own processor, one thread at a time. A brief bug capture converts in moments; a full-hour recorded meeting takes minutes and patience. Screen content compresses efficiently, which helps, but be realistic about long recordings and start them when the tab can be left alone.
Why does my WebM recording show no duration in the player?
Browser recorders stream data to the file as they capture, and many never go back to write the finished duration into the header. Players then show a blank or wrong length and seeking misbehaves. Converting to MP4 rebuilds the file with proper timing information, which usually cures the scrubbing weirdness too.
Can Premiere Pro open WebM files?
Not natively in most versions; Adobe's tools historically leaned on the MPEG codec family, leaving WebM to third-party plugins. Rather than installing workarounds on every machine, converting the recording once to H.264 MP4 gives you a file Premiere, Final Cut, Resolve, and everything else ingest without discussion.
Do WebM to MP4 converters work without an internet connection?
This one does once its engine has been fetched. The first visit downloads roughly 31 MB of WebAssembly, cached by the browser from then on, after which conversion needs no connectivity whatsoever. Recordings of sensitive internal systems can therefore be converted on machines that never let the file near a network.
Are there any usage limits?
None. Everything is generated locally in your browser, so there is no server cost, no metering, and no daily cap, use it as many times as you like, completely free.
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