WEBM vs MP4: which to use and when to convert
2026-10-06
WEBM and MP4 do the same job with different technology. MP4 normally carries H.264 video and AAC audio, both of which are patented formats that device makers license. WEBM was created by Google as an open, royalty-free alternative, using VP8 or VP9 video with Vorbis or Opus audio.
| WEBM | MP4 |
|---|
| Video codec | VP8, VP9 (sometimes AV1) | H.264, sometimes HEVC |
| Audio codec | Vorbis or Opus | AAC |
| Chrome, Firefox, Edge, Android | Plays | Plays |
| iPhone, iPad, Safari | Recent versions only | Plays |
| TVs, consoles, car screens | Rarely | Almost always |
| Video editors | Often not importable | Standard |
| Upload forms and messaging apps | Often rejected | Accepted |
Why you have a WEBM file
- A browser recorded it. Browser-based screen recorders and meeting tools save WEBM because that is what the browser's built-in recorder produces.
- It was downloaded from a website. Sites that serve video to browsers often use WEBM to save bandwidth.
- A screen-capture app defaulted to it.
WEBM to MP4
This is the common direction: the file needs to go somewhere that only takes MP4. WEBM to MP4 re-encodes the video to H.264 and the audio to AAC. If you only need the sound, WEBM to MP3 is much quicker, and WEBM to GIF turns a short recording into an animation.
One quirk of browser-recorded WEBM files: they are often written without a proper duration or seek index, so players cannot skip around in them. Converting to MP4 rebuilds the file and usually fixes this.
MP4 to WEBM
Converting the other way is mostly for web developers who want a smaller file for a background or autoplay video, with an MP4 as the fallback. On this site MP4 to WEBM produces VP8 video and Vorbis audio at a fixed video bitrate.
| Setting | Video bitrate |
|---|
| High | 2 Mbps |
| Medium | 1 Mbps |
| Small | 500 kbps |
Two honest caveats. First, VP8 is the older WEBM codec; VP9 and AV1 compress better but are too slow to encode in a browser tab. Second, the encoder runs in its fastest real-time mode. The result is a valid, widely playable WEBM, but a desktop VP9 encode will be smaller at the same quality. If you are optimising a production website, treat the output here as a quick draft.
Which one should you keep?
- Sending to people, uploading, editing: MP4.
- Embedding on your own website: offer both, WEBM first and MP4 as the fallback.
- Archiving a screen recording: keep the original WEBM and make an MP4 copy when you need one. Every conversion loses a little quality, so the original is the best master.
Transparency is one thing WEBM can do that MP4 cannot. A WEBM with a transparent background loses it when converted to MP4, and the transparent areas turn solid.
More guides
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