WebM to MP4: make browser recordings play everywhere
WebM files come from screen recorders, browser extensions, meeting tools and video downloads — and then refuse to open in the iPhone Photos app, QuickTime, iMovie or a TV’s media player. This WebM to MP4 converter fixes that in your browser: it re-encodes VP8, VP9 or AV1 video to H.264 and Opus or Vorbis audio to AAC, producing an MP4 that plays practically anywhere.
Nothing is uploaded, so recordings of meetings, dashboards or your screen stay private. And if all you need is a file ending in .mp4 for a browser or an Android phone, choose “Keep original” to copy the VP9 or AV1 stream into MP4 in seconds, without re-encoding.
How to use the WebM to MP4 Converter
- Drop your WebM files on the upload area, or click it to browse.
- Leave the codecs on H.264 and AAC for maximum compatibility, or switch both to “Keep original” for a quick rewrap.
- For a smaller file, set Resolution to 1080p or 720p and Quality to Medium.
- Press Convert to MP4 and follow the progress; each file reports when it is done.
- Play the MP4 beside the WebM to check it, then download it or a ZIP of every file.
WebM to MP4 Converter features
Plays on Apple devices
H.264 and AAC are what iPhone, iPad, QuickTime and iMovie expect, so the MP4 opens without extra apps.
PowerPoint and editor friendly
Microsoft recommends MP4 with H.264 video and AAC audio for videos in PowerPoint, and editing apps import it without plug-ins.
Odd sizes handled
Window recordings with an odd width or height lose one pixel column or row, because H.264 needs even dimensions; everything else keeps its exact size.
Optional instant rewrap
“Keep original” copies VP9 or AV1 with Opus into MP4 with no quality loss when the file only needs to be an .mp4.
Batch and ZIP
Convert a week of recordings in one go and save them together.
Why WebM files won’t open everywhere
WebM was created for web browsers: royalty-free VP8, VP9 or AV1 video and Vorbis or Opus audio in a container derived from Matroska. Browsers handle it well, which is why Chrome’s built-in recorder, many screen-capture extensions and online meeting tools save WebM by default.
Outside the browser, support is patchy. QuickTime Player, the iPhone Photos app, iMovie and Final Cut Pro don’t import WebM, and some TVs won’t play it. Even PowerPoint, which accepts WebM in recent versions, recommends MP4 with H.264 and AAC. H.264 in MP4, by contrast, has been the common language of video devices for well over a decade.
Re-encode, or keep the original codecs?
Vorbis audio is always converted to AAC, because MP4 players rarely support it.
| Setting | Speed | Quality | Plays on |
|---|---|---|---|
| H.264 + AAC (default) | Often faster than real time | Re-encoded at the quality you choose | Everything: iPhone, Android, Windows, Mac, TVs, editors |
| Keep original (VP9/AV1 + Opus in MP4) | Seconds | Identical to the WebM | Browsers and Android; not most Apple apps or editors |
| HEVC + AAC | Similar, where supported | Re-encoded; smaller than H.264 | Apple devices, recent Android; Windows may need an extension |
Tips for screen recordings
- Text and interface details stay crisper at a higher quality: choose High or Very high rather than lowering the resolution.
- Only need part of a long recording? Cut it first with the video cutter.
- For a looping animation in a chat or a README, Video to GIF works straight from the WebM.
- To email a long recording, shrink the MP4 afterwards with the video compressor.
WebM to MP4 Converter FAQ
How do I convert WebM to MP4?
Drop the WebM above and press Convert to MP4. With the default H.264 and AAC settings the result plays on nearly every device; download it when the progress bar finishes.
Why is the MP4 bigger than my WebM?
VP9 and AV1 compress more efficiently than H.264, so matching their quality takes more bits. Choose Medium quality or a lower resolution if size matters, or HEVC for a smaller file on Apple devices.
Can I convert WebM to MP4 without re-encoding?
Yes — set both codecs to “Keep original”. The VP9 or AV1 video and Opus audio are copied into MP4 in seconds. That file plays in browsers and on Android, but Apple’s apps and many editors still need H.264.
Will the MP4 play on my iPhone?
With the default H.264 and AAC, yes — save it to Files or Photos and it plays like any other video.
Is there a file size limit?
No limit is imposed. The practical ceiling is your device’s memory and storage, since the new file is built in the browser before you download it; long recordings convert fine on a typical computer.
Are my recordings uploaded?
Never. The converter code (Mediabunny, MPL-2.0) is downloaded the first time you add a file, and from then on everything happens on your device.