Vis Exo
CONVERT — WEBM TO MP4
WebM to MP4 Converter, Free, In Your Browser
A screen recording, a browser capture or a download from a web tool arrives as WebM — and then nothing will open it. Not QuickTime, not your phone, not the editor you actually need. Drop it here and it comes back as an ordinary MP4 with H.264 video and AAC audio.
WebM Is a Web Format, Not a File Format
Nothing Apple will play
WebM carries VP8 or VP9 video, which QuickTime, Photos, iMovie and every iOS app refuse to open. Instagram, TikTok and most upload forms reject it too. H.264 inside an MP4 is what all of them accept.
A real re-encode, not a rename
Because the video codec itself has to change, this is a genuine transcode: frames are decoded and re-encoded as H.264. Your device does the encoding — through its own video hardware where the browser exposes it — so a laptop usually runs faster than real time.
The audio comes along
WebM soundtracks are normally Opus, which MP4 players will not play. Audio is converted to AAC in the same pass, so you get picture and sound together instead of a silent file.
You can check it before saving
The converted file plays back in the page as soon as it finishes, so you can confirm the picture and the sound are right before it lands in your downloads folder.
Three Steps, In Your Browser
- 1
Drop the WebM in
Choose the file or drag it onto the box. It is read from your own disk — nothing is uploaded, which is exactly why there is no size cap and no queue to wait in.
- 2
Leave the target on MP4
MP4 with H.264 and AAC is selected by default. Keep the original resolution unless you want a smaller file too, in which case 720p is the sweet spot for screen recordings.
- 3
Convert and save
Press Convert Video, watch the progress, then play the result and save it. Screen recordings are mostly static, so they usually convert faster than people expect.
WebM to MP4 on iPhone, Mac, Windows and Android
The same page works everywhere, with nothing to install. What differs is where the file comes from and where it goes.
iPhone & iPad
Open this page in Safari, tap the box and pick the WebM from Files. The MP4 saves straight to Files or Photos and plays in the Photos app.
Mac
Works in Safari, Chrome and Edge. The MP4 opens in QuickTime, iMovie and Final Cut without any plug-in.
Windows
Chrome or Edge convert fastest, using your graphics chip to encode. The result plays in the built-in Photos and Films & TV apps.
Android
Chrome on Android handles it; short screen recordings convert in seconds, and the MP4 lands in your Downloads.
MP4, WebM, or Just the Audio?
Three options, honestly compared — including when the right answer is to convert nothing at all.
| Target | Pick it when | Watch out for |
|---|---|---|
| MP4 — H.264 + AAC | Uploading anywhere, editing in any app, or playing on a TV, console or iPhone. | Audio is re-encoded to AAC; the picture is copied when it is already H.264. |
| WebM — VP9 + Opus | Publishing on the web, where every current browser plays it. | Some editors and older devices cannot import VP9, so it is a poor hand-off format. |
| MP3 — audio only | You only need the soundtrack, a voice note or a podcast pull. | Drops the picture entirely; not a way to make a smaller video. |
WebM to MP4 FAQ
Can I convert WebM to MP4 without uploading it?
Yes, and that is the whole point of this one. The file is decoded and re-encoded by your own browser, so it never goes to a server and there is no upload size limit to hit.
Why will my phone not play WebM files?
Apple platforms have never supported VP8 or VP9 video in their built-in players. Converting to H.264 in an MP4 container makes the same footage play natively, with no app needed.
Will the MP4 be bigger than the WebM?
Usually a little, at matching quality, because VP9 compresses slightly better than H.264. Dropping the resolution to 720p normally more than makes up for it if size matters.
Does it keep the audio?
Yes. WebM audio is typically Opus, which is converted to AAC for the MP4. If your browser cannot encode AAC at all, the page warns you before you start rather than handing you a silent video.
Is there a length limit?
No, and no paid tier either. The practical limits are your device memory and your patience, since the conversion happens locally rather than on a server farm.
Related Converters
MOV to MP4
QuickTime files that already hold H.264 and AAC are re-wrapped rather than re-encoded — near-instant, with nothing lost.
MKV to MP4
Matroska is the archive container, and its contents are frequently H.264 and AAC already — so the conversion is usually a lossless re-wrap.
MP4 to WebM
The other direction: a finished MP4 turned into a smaller, royalty-free WebM for a web page, a loop or an embed.
Compress a Video
Keep the format, drop the resolution and the bitrate — the same engine that converts also makes files smaller.
Convert it, then track something in it
Vis Exo adds blob tracking, pose skeletons, trails, LUT grades and captions to the finished MP4 — free, and entirely in your browser.