Format at a glance
- Full name
- WebM Media Container
- File extensions
- .webm
- MIME types
- video/webm
- Category
- Video
- Compression
- Depends on the contained codec
- Transparency
- Not applicable
- Animation
- Not applicable
- Properties
- Multiple media tracks, Subtitles
Suitable tools
What is this format?
WebM uses a constrained form of the Matroska container. It stores media tracks and timing information, while video and audio codecs perform the actual compression.
VP9 with Opus is a common modern combination. VP8 and Vorbis are older compatible options; AV1 can also appear in WebM, but LocalFileLab does not currently offer AV1 as a WebM output.
What is it used for?
- HTML5 video on websites
- Screen recordings created by browsers
- Web-oriented video downloads
- Audio and video using open codecs
Which programs can open it?
- Chrome, Firefox, Edge and other Chromium browsers
- VLC, mpv and FFmpeg-based players
- DaVinci Resolve and editors with WebM support
- Browser-based recording and streaming tools
Support across devices and browsers
Current browsers and flexible players support WebM; some older desktop programs need extensions.
Current browsers play WebM, while older QuickTime-oriented software can be limited.
Browsers and players broadly support WebM and its common open codecs.
Chrome and many media apps support WebM with VP8 or VP9.
Recent Safari versions support important WebM combinations; older devices and apps may remain limited.
WebM is particularly well supported in current Chromium and Firefox browsers; the actual codec combination still matters.
Advantages
- Designed for web playback and open-codec workflows
- VP9 and Opus provide good compression efficiency
- Broad support in current desktop browsers
Disadvantages
- Less universal than MP4 in older hardware and editing software
- Safari and iOS support depends more strongly on version and codec
- The extension does not reveal whether VP8, VP9 or another codec is present
Comparison with alternatives
MP4 with H.264/AAC is usually more device-compatible, while WebM focuses on open, web-oriented codecs.
MKV accepts a wider range of tracks and codecs; WebM narrows these choices for web compatibility.
WebM is much more efficient for long or colorful animation but must be embedded as video.
LocalFileLab support
WebM can be read locally through browser features or FFmpeg/WebAssembly; the decoder remains codec-dependent.
VP8 or VP9 video and Opus or Vorbis audio are configured WebM output options.
Codec, CRF, dimensions, frame rate and audio settings can be changed locally.
Current browsers can play supported WebM codec combinations directly and locally.
Metadata is configurable, but complex track layouts, chapters and subtitles are not fully preserved.
Container and codecs
The LocalFileLab statements below come from the FFmpeg/WASM and WebCodecs paths actually configured in the repository. Decoders or tracks not explicitly evidenced in code are marked unverified.
- Container
- WebM
- Typical video codecs
- VP8, VP9, AV1
- Typical audio codecs
- Opus, Vorbis
| Codec | Type | Input | Output | Notes |
|---|---|---|---|---|
| VP8 | Video | Unverified | Supported | The project does not enumerate the FFmpeg/WASM input decoder per codec. A concrete FFmpeg/WASM encoder is configured in the repository. |
| VP9 | Video | Unverified | Supported | The project does not enumerate the FFmpeg/WASM input decoder per codec. A concrete FFmpeg/WASM encoder is configured in the repository. WebCodecs is probed at runtime and FFmpeg/WASM remains the fallback. |
| AV1 | Video | Unverified | Not supported | The project does not enumerate the FFmpeg/WASM input decoder per codec. This codec is not offered as an output for this container. |
| Opus | Audio | Unverified | Supported | The project does not enumerate the FFmpeg/WASM input decoder per codec. A concrete FFmpeg/WASM encoder is configured in the repository. WebCodecs is probed at runtime and FFmpeg/WASM remains the fallback. |
| Vorbis | Audio | Unverified | Supported | The project does not enumerate the FFmpeg/WASM input decoder per codec. A concrete FFmpeg/WASM encoder is configured in the repository. |
| Text and subtitle tracks | Subtitle | Unverified | Not supported | This track is not mapped explicitly during export. |
Tracks and metadata
- Subtitle tracks
- Unverified
- Multiple audio tracks
- Not supported
- Chapters
- Unverified
- Metadata
- Configurable
Known combinations
A concrete FFmpeg/WASM encoder is configured in the repository. WebCodecs is probed at runtime and FFmpeg/WASM remains the fallback.
A concrete FFmpeg/WASM encoder is configured in the repository.
This codec is not offered as an output for this container.
Related formats
Frequently asked questions
Is WebM the same as VP9?
No. WebM is the container and VP9 is one possible video codec inside it. A WebM file may also contain VP8.
Why does WebM fail in some applications?
Some older or production-focused applications do not fully support the container or the open codecs stored inside it.
Is WebM better than GIF for websites?
For longer, large or colorful animation, WebM is normally much smaller and higher quality, but it requires a video element.