Convert to and from WebM, free.
WebM is the open, royalty-free container built for the web. It is what most browser-based screen recorders produce, and VP9 packs the same picture into noticeably less data than H.264.
Convert something else to WebM
Pick what you have. Each page opens the editor with WebM already selected as the output.
Convert WebM to something else
Pick where it is going. Most editing software, phones and TVs will not open a WebM file.
What WebM actually is
WebM (Matroska-based)
VP8 / VP9 / AV1 video, Opus audio
Web embeds and browser recordings
Chrome, Firefox and Edge; hit and miss elsewhere
Very small at the same quality
Streams natively in Chrome, Firefox and Edge with no plugin.
VP9 delivers smaller files than H.264 at the same visual quality, which cuts bandwidth on a busy page.
Most editing software, phones and TVs will not open a WebM file.
Social platforms and messaging apps frequently reject the extension outright.
Safari and older Apple devices handle WebM inconsistently.
Questions about WebM
What is a WebM file?
WebM is the open, royalty-free container built for the web. It is what most browser-based screen recorders produce, and VP9 packs the same picture into noticeably less data than H.264. It is the WebM (Matroska-based) container, usually holding VP8 / VP9 / AV1 video, Opus audio.
Is converting WebM free?
Yes. Convert and preview for free, then create a free account to download the result. Nothing is installed and there is no watermark on the file itself.
Will converting to WebM lose quality?
Some, whenever the codec changes: every re-encode discards detail. Where the container can simply be rewritten around the existing streams it is lossless, and where it cannot the default settings are chosen so the loss is not visible at normal viewing size.
Other formats
Converters
Convert it, then keep editing.
Every converter opens the full editor, so you can trim, caption and share without uploading the file twice.