What Is WebM?
WebM is an open, royalty-free video file format developed by Google and released in 2010. It was designed specifically for use on the web, offering high-quality video at small file sizes without requiring any licensing fees. If you've ever watched a video embedded directly on a webpage without relying on a plugin like Flash, there's a good chance it was delivered as a WebM file.
How WebM Works
WebM is essentially a container format — it wraps together video, audio, and metadata into a single file. Inside that container, it uses specific codecs:
- Video codecs: VP8 or VP9 (developed by Google), or the newer AV1 codec
- Audio codecs: Vorbis or Opus
- Container format: Based on the Matroska (MKV) multimedia container
The VP9 codec, in particular, delivers compression efficiency comparable to H.265/HEVC — meaning you get excellent picture quality at roughly half the file size of older formats like H.264.
Who Created WebM and Why?
Google acquired On2 Technologies in 2010 and released the VP8 codec as open source. This move was aimed at creating a truly open standard for web video — one that any browser, device, or platform could implement for free without paying codec royalties. WebM was the result of that effort.
The goal was simple: give the web a universal, patent-free video format that could replace proprietary alternatives and work seamlessly with HTML5.
What Are WebM Files Used For?
WebM is commonly used in several scenarios:
- Web-embedded video: Streaming video directly in a browser via the HTML5
<video>tag - Animated clips: Used as an alternative to GIFs — much smaller file sizes, better quality
- Online video platforms: YouTube uses VP9/WebM as one of its primary delivery formats
- Video conferencing: Opus audio (part of WebM) is widely used in real-time communication
Which Browsers Support WebM?
WebM enjoys broad support across modern browsers:
| Browser | WebM / VP8 | WebM / VP9 |
|---|---|---|
| Google Chrome | ✅ Yes | ✅ Yes |
| Mozilla Firefox | ✅ Yes | ✅ Yes |
| Microsoft Edge | ✅ Yes | ✅ Yes |
| Safari | ⚠️ Limited | ⚠️ Limited |
| Opera | ✅ Yes | ✅ Yes |
Note: Safari's WebM support has historically been limited, which is why many developers provide an MP4 fallback alongside WebM files.
WebM vs. Other Formats at a Glance
- vs. MP4: WebM is open and royalty-free; MP4 uses H.264/H.265 which require licensing
- vs. AVI: WebM is far better suited for the web — smaller sizes, streaming-friendly
- vs. GIF: WebM produces dramatically smaller files with better color depth and quality
Should You Use WebM?
If you're a web developer, content creator, or anyone publishing video online, WebM is worth understanding and using. Its combination of open licensing, excellent compression, and native browser support makes it one of the most practical formats for modern web video. The main caveat is Safari compatibility — a solvable issue by providing an MP4 fallback.
In the sections that follow across this site, you'll learn how to create, convert, compress, and embed WebM files step by step.