Theora to WebM (VP9) - Online Video Converter
Convert Theora to WebM (VP9) online. Private, client-side - no uploadrequired. Batch conversion, quality presets, codec control.
About Theora to WebM (VP9)
Convert Theora to WebM. Theora is Xiph's open video codec paired with Vorbis audio. WebM pairs VP9 video with Opus audio and supports an alpha channel. Apple editors accept it unevenly; keep MP4 for editing round-trips..
Why convert Theora to WebM (VP9)?
- Smaller files with WebM lossy compression.
- Keep animation and transparency where supported.
- Private, no upload - runs in your browser.
Theora vs WebM (VP9)
| Animation | Yes | Yes |
|---|---|---|
| Transparency | No | Yes |
| Compression | lossy | lossy |
| Typical use | Theora is Xiph's open video codec paired with Vorbis audio. | WebM pairs VP9 video with Opus audio and supports an alpha channel. |
When not to convert Theora to WebM (VP9)
- Skip WebM for archival masters: lossy compression discards detail, so keep the Theora original.
- Keep a master copy: repeated exports stack small losses, so archive Theora before batch WebM shares.
Limits
Starting point: Theora - Theora is Xiph's open video codec paired with Vorbis audio. Ogg multiplexing quirks can offset sync; verify after conversion. Apple editors accept it unevenly; keep MP4 for editing round-trips. Encode WebM (VP9 / Opus) from Theora at a bitrate near the source, and confirm the audio track before converting.
How conversion works
Conversion runs entirely in your browser with FFmpeg WASM. Files never leave your device.