How to use the WebM to MP4 tool
- Choose the video you want to convert.
- Leave "Fast mode" on when it appears: it changes the container without re-encoding, so it is instant and lossless. Otherwise pick a quality.
- Press Convert.
- Preview the result and download it.
About this tool
WebM (an open, royalty-free web format from Google, based on Matroska) usually holds VP8, VP9, AV1 video with Opus, Vorbis audio and is best known for websites, web apps and Android. Works when the video inside is VP8, VP9 or AV1 with Opus or Vorbis audio, which is what almost every WebM file contains.
MP4 with H.264 video and AAC audio is the closest thing to a universal video format. It plays on iPhones, Android phones, Windows, macOS, smart TVs and game consoles, uploads to every social platform, and previews inline in email and chat apps.
Going from WebM to MP4 needs the video to be decoded and re-encoded (to H.264, with AAC audio where your browser can encode it). Your browser's hardware encoder does the work, and the bitrate is capped so the new file is not larger than it needs to be.
Common reasons to convert WebM to MP4
- Opening a browser screen recording (many web recorders save WebM) in iMovie, Premiere, Final Cut or a phone gallery that does not read WebM.
- Sending a clip to people with iPhones, smart TVs or older devices that expect MP4.
- Uploading to a platform or form that only accepts MP4.
WebM vs MP4 at a glance
| WebM | MP4 | |
|---|---|---|
| What it is | an open, royalty-free web format from Google, based on Matroska | MPEG-4 Part 14 |
| Typical video codecs | VP8, VP9, AV1 | H.264, HEVC, AV1 |
| Typical audio codecs | Opus, Vorbis | AAC, MP3 |
| Best for | Websites, web apps and Android | Sharing, social platforms, phones, TVs and email |
| Plays on | Chrome, Edge, Firefox, Android, recent Safari | Practically everywhere |
Why use ToolsCrow for this
- Hardware-accelerated. Uses your device's video encoder.
- Private. Files never leave your device.
- No watermark. Free, no account.
- Honest errors. Unsupported codecs are explained, not hidden.
Good to know
- Works when the video inside is VP8, VP9 or AV1 with Opus or Vorbis audio, which is what almost every WebM file contains.
- Output is H.264 video with AAC audio (or Opus if your browser cannot encode AAC).
Frequently asked questions
Is my video uploaded to a server?
No. Everything runs inside your browser tab using your own device's video hardware. Your file is never sent to ToolsCrow or anyone else, which also means there is no waiting for an upload and it keeps working if your connection drops after the page has loaded.
Is it really free? Is there a watermark?
It is free with no sign-up, no watermark and no daily limits. The only limits are the ones your device sets: memory and processing power.
How large a video can I use?
Because the video is processed on your device, the limit is your device's memory rather than a server quota. Phone clips of several hundred MB are fine on most devices, and desktop computers usually handle 1 to 2 GB. Files over about 4 GB are not supported.
Which browsers work best?
Current Chrome, Edge and Safari (16.4 or newer, including iPhone and iPad) work best because they include the WebCodecs video engine. Recent Firefox versions work for many files. Older browsers fall back to a much slower real-time mode or may not work at all.
Will converting WebM to MP4 reduce quality?
Any re-encode costs a little quality in theory. The High preset is tuned to be visually indistinguishable, and the bitrate is capped to the original so the file does not grow pointlessly.
What is the difference between WebM and MP4?
WebM is an open, royalty-free web format from Google, based on Matroska, best for websites, web apps and Android. MP4 is MPEG-4 Part 14, best for sharing, social platforms, phones, TVs and email.
Why does my result have Opus audio instead of AAC?
Some browsers (for example Chrome on Linux) cannot encode AAC audio. When that happens the tool saves Opus audio instead and tells you. Opus plays in Chrome, Firefox, Edge, VLC and recent Safari; if you need AAC everywhere, run the tool in Chrome or Edge on Windows or macOS, or in Safari.
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