Convert MP4 to WebM
WebM is the web's open video format: VP9 video and Opus sound, both royalty-free. It's what a web page offers beside an MP4, and what you need when a site or a tool asks for WebM.
Your file never leaves this device. Everything runs in your browser.
How it works
- Drop your video.
- Pick the format you need. The tool says which parts it copies and which it re-encodes.
- Press Convert and download the new file.
Questions
Why does MP4 to WebM always re-encode?
A WebM can't hold H.264 or AAC, the codecs almost every MP4 uses, so the video is re-encoded to VP9 and the sound to Opus. It takes a while and works on videos up to 15 minutes.
Which browsers can make a WebM?
Chrome and Edge have the VP9 and Opus encoders it needs. If your browser doesn't, the tool says so before it starts, and you can make an MP4 instead.
Which formats can I convert to?
MP4 and MOV with H.264 video and AAC sound, and WebM with VP9 video and Opus sound: the formats a browser can write. AVI, FLV and WMV aren't offered, because no browser can make them.
Does converting lose quality?
Not when the video is copied: a MOV or MKV holding H.264 becomes an MP4 without its picture being touched. When the codec has to change, the video is re-encoded at high quality, and like any re-encode it isn't bit-for-bit the original.
Is there a length limit?
Files up to 2 GB. A conversion that copies the video has no length limit; one that re-encodes it takes videos up to 15 minutes.
What happens to subtitles and extra audio tracks?
The new file gets the main video and the main sound. Subtitle tracks and extra languages, which an MKV often carries, are left out.
Does my video get uploaded?
No. It's converted in your browser, on your device.
Which browsers does it work in?
Current Chrome, Edge, Safari and Firefox. Re-encoding to MP4 or MOV needs a browser that can encode H.264, which Chrome, Edge and Safari can. Making a WebM needs VP9 and Opus encoders, which Chrome and Edge have. If yours can't, the tool says so before it starts.