How to use the WEBM Converter converter
- Add filesClick “Choose Files” or drag them in. Each file is detected automatically, and you can mix different formats in one batch.
- Pick the output formatUse the “to” menu next to each file to choose the target format (WEBM is preselected).
- Convert and saveHit “Convert”. Everything is processed on your device, then you can download each result or a ZIP of all of them.
About WEBM
WEBM WebM Video
WebM is an open, royalty-free format designed for the web. Browsers and screen recorders often produce it, but iPhones, QuickTime and many video editors handle it poorly.
- Compression
- Lossy (VP8/VP9/AV1)
- Features
- Video + Opus/Vorbis audio
- Origin
- 2010, Google
- Best for
- Web video, screen recordings
Why use ConvertMathly?
Files are processed on your device and never uploaded. Close the tab and they are gone.
No account, no daily cap, no queue and no watermark — convert as much as you want.
The same engine used by professional video tools, running in your browser via WebAssembly.
Windows, Mac, Linux, Chromebook, iPhone and Android — any modern browser, nothing to install.
Frequently asked questions
What formats does the WEBM Converter support?
It accepts MP4, MOV, AVI, MKV, WEBM, FLV, WMV, 3GP, M4V, MPEG, MPG, TS, MTS, M2TS and more, and can output MP4, WEBM, MOV, AVI, MKV, FLV, WMV, 3GP, GIF, MP3, WAV, AAC, OGG, M4A, FLAC.
Is it really free?
Yes. ConvertMathly is free with no sign-up, no watermarks and no limits. The site is supported by ads.
Are my files private?
Completely. Conversion happens inside your browser — files are never uploaded to any server.
Why does the first video or audio conversion take longer?
A one-time download of the FFmpeg engine (~30 MB) is needed. It is cached afterwards, so later conversions start instantly.
Does it work on iPhone and Android?
Yes, the converter works in Safari, Chrome, Firefox and Edge on phones, tablets and computers.