WebM
The open, royalty-free video container Google launched for the web. Browser screen recordings produce it, and YouTube delivers much of its video in its codecs.
WebM is an open video container — the file wrapper, like MP4 or MOV. It holds VP8, VP9 or AV1 video and Opus or Vorbis audio, all royalty-free. Chrome, Firefox and Edge play it; for maximum compatibility, especially on Apple devices, MP4 with H.264 is still the safe choice.
What is WebM?
WebM is a video file format Google introduced in 2010 for the web, based on the Matroska (MKV) container. It defines which codecsCodecThe algorithm that compresses and decompresses video — H.264, H.265 (HEVC) and AV1 are the most common in modern streaming.Open definition → it can hold: VP8, VP9 or AV1AV1The open, royalty-free codec: about 40% less data than H.264 for the same picture, in exchange for heavier encoding.Open definition → for video and Vorbis or Opus for audio. All of them are open and royalty-free.
A container and a codec are different things. The container is the wrapper that keeps the video and audio tracks with their metadata; the codec compresses each track. That is why two WebM files can differ a lot in quality and size.
Where you meet WebM
Screen and camera recordings made in the browser with the MediaRecorder API usually come out as WebM, and so do many web capture tools. YouTube uses VP9, one of the WebM codecs, for much of its video. WebM is also used for short animations on websites as a lighter alternative to GIF.
WebM vs MP4
| WebM | MP4 | |
|---|---|---|
| Video codecs | VP8, VP9, AV1 | H.264, HEVC, AV1 |
| Audio codecs | Opus, Vorbis | AAC, MP3, Opus |
| Licensing | Royalty-free | Depends on the codec |
| Browsers | Chrome, Firefox, Edge; Safari depending on version and codec | All |
| Editing software | Uneven support | Practically all |
If the video must play on every device, MP4 with H.264H.264 (AVC)The most compatible video codec: practically every browser, phone and smart TV plays it. The safe format to upload and deliver.Open definition → is still the safe choice.
How to convert WebM to MP4
Free for Windows, macOS and Linux. Open the WebM, choose MP4 as the format and H.264 as the video codec.
A command-line tool for converting batches of files or automating it on a server.
If the video is going to be published, the platform transcodesTranscodingRe-encoding a source video into multiple resolutions and bitrates so a player can switch between quality levels on the fly.Open definition → the original into delivery formats.
Further reading
- The WebM Project — the official site of the format.
- Codec — the difference between a codec and a container.
