WebM (WebM Video)
Google's open, royalty-free video format built for the web.
| Full name | WebM Video |
| Extension | .webm |
| MIME type | video/webm |
| Developer | Google (with On2 Technologies, Xiph, and the Matroska project) |
| Released | May 19, 2010 |
| Type | Video container format |
| Video codecs | VP8, VP9, AV1 |
| Audio codecs | Vorbis, Opus |
What is a WebM file?
WebM is an open, royalty-free video format designed for use on the web. Google announced it at Google I/O on May 19, 2010, alongside the open-sourcing of the VP8 video codec. It works in all major browsers without licensing fees.
WebM is a container format based on a subset of the Matroska (MKV) specification. It pairs VP8 or VP9 video (and more recently AV1) with Vorbis or Opus audio. Because every part of the format is patent-unencumbered and freely licensed, anyone can implement it without paying royalties. HTML5 video elements support WebM natively in Chrome, Firefox, and Edge.
History
Google acquired On2 Technologies in February 2010 for about $124.6 million, gaining ownership of the VP8 video codec. That May, Google open-sourced VP8 under a BSD-style license and released the WebM container format at Google I/O, with Mozilla, Opera, and over forty other companies joining the project from day one. VP9 support was added in 2013, and AV1 support followed later, keeping WebM relevant as video quality demands grew.
Container vs codec
WebM files use the Extensible Binary Meta Language (EBML) encoding inherited from Matroska. The file is organized into a header segment and one or more clusters that hold the actual audio and video data blocks. Each block carries a timestamp and codec-specific data. Because WebM is a strict profile of Matroska, most Matroska tools can read WebM files, though WebM deliberately excludes some Matroska features to stay lightweight.
What it is used for
- Embedding video on websites without relying on proprietary formats
- Storing screen recordings and tutorial videos for web delivery
- Streaming video in browsers via the HTML5 <video> element
- Distributing open-source or Creative Commons video content
How to open it
WebM files play in Google Chrome, Mozilla Firefox, Microsoft Edge, and VLC without any extra plugins. On Windows, the codec pack from the WebM project adds playback support to Windows Media Player and other DirectShow-based players.
Pros and cons
Strengths
- Completely royalty-free with no per-unit licensing costs
- Good compression at smaller file sizes compared to older formats like AVI
- Native support in all major desktop browsers with no plugins needed
- Flexible codec support: VP8, VP9, and AV1 all fit inside the same container
Trade-offs
- Limited native support on Apple devices; Safari added VP9/WebM support only in 2020
- VP8 and VP9 encoding is slower than H.264 at equivalent quality
- Less widely supported in professional video editing software than MP4
- Smaller ecosystem of hardware decoders compared to H.264
Convert WebM files
Free, in your browser, no signup. Start at the WebM converter, or jump straight to a popular conversion below.
From WebM
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WebM FAQ
Is WebM the same as MKV?
WebM is based on a restricted profile of the Matroska (MKV) format, so they share the same underlying EBML structure. MKV supports far more codecs and features; WebM is a smaller, stricter subset aimed specifically at web delivery.
Can I play WebM files on iPhone or iPad?
iOS and iPadOS do not support WebM natively in the Safari browser. You can play WebM on Apple devices using third-party apps like VLC, or convert the file to MP4 first.
Which is better for web video: WebM or MP4?
Both work well. MP4 with H.264 has broader device support, including older iPhones and Smart TVs. WebM with VP9 or AV1 often produces smaller files at the same quality, which matters for bandwidth. Many sites serve both and let the browser pick.
Does WebM support subtitles and chapters?
Yes. Because WebM inherits its structure from Matroska, it can store subtitle tracks (WebVTT is the recommended format inside WebM) and chapter markers alongside the video and audio.