Convert video
Convert a video between MP4, WebM, MKV and MOV — pick maximum compatibility for a re-encode that plays everywhere, or a fast lossless remux that only changes the container. Conversion runs entirely in your browser; nothing is uploaded.
Open Convert video →What is Convert video?
A free, private video converter that reads MP4, M4V, MOV, MKV, WebM and MPEG-TS files and writes any of four containers — MP4, WebM, MKV or MOV — entirely in your browser. Drop a file and it tells you what it is straight away: container, resolution, length and the codecs inside. Best compatibility re-encodes to the most widely-playable codecs the target container supports, checked against what your own browser can actually encode. Fastest instead copies any track the target container can already hold, so the conversion becomes an instant, lossless remux and only the container changes. Before you click, a line under the controls says which of the two you are about to get. Everything runs on the browser's WebCodecs engine on your own device — nothing is uploaded, there is no file-size limit, and no watermark is added.
How to use Convert video
- Load a video — Drop an MP4, MOV, MKV, WebM, M4V or TS file onto the tool, or click to choose it. Its container, resolution, length and codecs appear under the player.
- Choose the output format — Pick MP4, WebM, MKV or MOV. MP4 plays almost everywhere, WebM is the web-native choice, MKV holds nearly any codec, and MOV is the QuickTime and editing-suite format.
- Choose the mode — Best compatibility re-encodes to the safest codecs for that container. Fastest copies the tracks that already fit and only rewrites the container. The hint line tells you which tracks will be copied and which re-encoded.
- Convert and download — Click Convert, watch the progress, preview the result in the player and save the file.
Frequently asked questions
Is my video uploaded to a server?
No. The conversion runs inside your browser with WebCodecs, using your own device's video hardware. It works offline and there is no size limit.
When is a conversion lossless?
In Fastest mode, whenever the source tracks already use codecs the target container can hold — H.264, HEVC, AV1, AAC, MP3 and the rest are copied byte for byte and only the container is rewritten. Converting between MP4, MOV and MKV is usually instant for this reason. WebM is the exception in both directions: it holds only VP8, VP9, AV1, Opus and Vorbis, so anything else has to be re-encoded.
Which output format should I pick?
MP4 for sharing, e-mail, phones and TVs. WebM for embedding in a web page. MKV when you want to keep unusual codecs or several tracks. MOV when an editing suite or an Apple workflow expects it.
Which input formats work?
MP4, M4V, MOV, MKV, WebM and MPEG-TS containers, with any codec your browser can decode. Rare professional codecs such as ProRes are not decodable in browsers and will not convert.
Can it convert AVI, WMV or FLV files?
No, and neither can any other in-browser converter — browsers ship no decoder for those containers, so they cannot be opened at all. The tool says so plainly instead of failing part-way through. Converting them needs desktop software.
Why does it not offer every codec?
Because the honest answer depends on your browser. The tool asks the browser which codecs it can genuinely encode at your video's resolution, intersects that with what the container legally holds, and picks the most compatible survivor — rather than offering a menu of options that might fail.
Tips
- Converting a screen recording (WebM) to MP4 makes it attach-and-play in e-mail and chat apps.
- Just need a MOV renamed into MP4-compatible form? Choose Fastest — Apple MOVs usually carry H.264 and AAC already, so it remuxes in seconds with no quality loss at all.
- Watch the hint line: if it says the tracks are copied unchanged, the conversion will finish almost instantly however long the video is.
- Compress and convert in one go: run the file through Compress video instead and pick the format there.