How to use the MP4 to WebM 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
MP4 (MPEG-4 Part 14) usually holds H.264, HEVC, AV1 video with AAC, MP3 audio and is best known for sharing, social platforms, phones, TVs and email. Works when the video inside is H.264, AV1, or HEVC (HEVC depends on your device), with AAC or MP3 audio.
WebM is an open, royalty-free format made for the web. VP9 video in WebM usually makes smaller files than H.264 at the same quality, and it is supported by Chrome, Edge, Firefox, Android and recent Safari. It is a strong choice for video embedded on your own website.
Going from MP4 to WebM needs the video to be decoded and re-encoded (to VP9, with Opus audio). 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 MP4 to WebM
- Embedding a video on your own website, where VP9 in WebM usually loads faster than H.264 at the same quality.
- Uploading to Wikimedia Commons and other open-media sites, which accept WebM but not H.264 MP4.
- Working with royalty-free codecs in open-source or web-app projects.
MP4 vs WebM at a glance
| MP4 | WebM | |
|---|---|---|
| What it is | MPEG-4 Part 14 | an open, royalty-free web format from Google, based on Matroska |
| Typical video codecs | H.264, HEVC, AV1 | VP8, VP9, AV1 |
| Typical audio codecs | AAC, MP3 | Opus, Vorbis |
| Best for | Sharing, social platforms, phones, TVs and email | Websites, web apps and Android |
| Plays on | Practically everywhere | Chrome, Edge, Firefox, Android, recent Safari |
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 H.264, AV1, or HEVC (HEVC depends on your device), with AAC or MP3 audio.
- Output is VP9 video with Opus audio.
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 MP4 to WebM 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 MP4 and WebM?
MP4 is MPEG-4 Part 14, best for sharing, social platforms, phones, TVs and email. WebM is an open, royalty-free web format from Google, based on Matroska, best for websites, web apps and Android.
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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