WEBM Converter
FileFlip converts WEBM files into 30 other formats entirely inside your browser, using WebCodecs and FFmpeg compiled to WebAssembly. The WEBM file is never uploaded to a server: it is read off your disk, converted on your own machine, and saved back by the browser. There is no file-size limit and no account to create.
How do I convert a WEBM file?#
- Drop your WEBM file onto the converter at the top of this page, or click it to pick one from your computer.
- Choose the format you want out of it. FileFlip downloads the engine that conversion needs, once, and your browser caches it.
- Conversion starts the moment you pick the format, and the result is yours to download. The work happens in this tab, so nothing is uploaded and nothing is queued.
Is it safe to convert WEBM files online?#
Yes, because nothing is uploaded. FileFlip converts WEBM files inside the browser tab you already have open, using WebAssembly builds of the same engines a desktop converter would install. Your file is read from your own disk into the page's memory, and no request carrying it is ever made.
You do not have to take that on trust. Open your browser's network panel, run a conversion, and you will see the engine come down and your file go nowhere. There is no upload, no server-side copy, no retention window, and no account tied to what you converted.
How FileFlip works lists every engine, its version and its download size, and shows how to check for yourself that nothing leaves your machine.
What happens to a WEBM file#
FileFlip converts WEBM into 30 formats with WebCodecs and FFmpeg, all of it inside the browser tab. Each conversion below names the engine it uses, what it downloads, and exactly what that conversion keeps or drops.
| Category | Video Files |
|---|---|
| File extension | .webm |
| FileFlip support | Read and written |
| Conversions available | 30 |
| Engines | WebCodecs and FFmpeg |
| Downloaded to your browser | 30.8 MB on the first conversion, then cached |
What is a WEBM file?#
A WEBM file holds VP8, VP9 or AV1 video with Vorbis or Opus audio in a cut-down version of the Matroska container, restricted to codecs that carry no patent licensing so browsers can play them freely.
Choose WebM when the video is going on a web page and you want it to play in browsers without a codec licence attached to it.
Convert WebM to MP4 when the file has to leave the browser, whether that is an edit timeline, an older iPhone or a television.
The WEBM file format reference covers the specification, the programs that open one, and what each conversion keeps or drops.
WEBM questions people ask#
Why did my screen recording save as a WEBM file?
Browser-based recorders and screen capture tools save WEBM because it is what the browser can encode without licensing anything. Recording in the browser goes through the MediaRecorder API, and VP8 or VP9 in WebM is the combination browsers ship by default, since encoding H.264 would mean paying for the patents. The recording is fine, it just needs converting before most editing software will take it.
What is the difference between WebM and MKV?
WebM is a deliberately narrowed version of Matroska. It uses the same container structure but only allows VP8, VP9 or AV1 video with Vorbis or Opus audio, where MKV takes any codec at all. That restriction is the point: a browser can support WebM completely, whereas supporting MKV would mean supporting every codec ever put in one.
Does converting WebM to MP4 lose quality?
Converting WebM to MP4 usually re-encodes the video and loses a little quality, because the VP9 or VP8 inside a WebM is not what MP4 players expect to find. MP4 can technically carry VP9 and AV1 now, but almost nothing in the wild plays those from an MP4, so a real conversion means encoding to H.264. Going the other way, MP4 to WebM, always re-encodes too, since H.264 is not allowed inside WebM at all.
Can WebM video have a transparent background?
WebM is one of the few video formats that carries transparency, using an alpha channel alongside VP9. That makes it the usual way to put video over a web page without a rectangular black box around it. The transparency does not survive conversion to MP4, since H.264 in MP4 has no alpha channel to put it in.
Does WebM play on iPhone?
WebM plays on recent iPhones and not on older ones. Safari had no WebM support for years, gained partial support along the way, and only reached full support in Safari 16 on macOS and iOS 17.4 on the phone. Anything older shows an empty player. VLC for iOS plays WebM regardless of the iOS version, and converting to MP4 avoids the question entirely.