Which format should I pick?

MP4, unless something specific told you otherwise. It is the only one you can send to a stranger and be confident it opens.

Does converting lose quality?

It does whenever the video has to be encoded again, which is most of the time. Where the existing frames can simply be moved into the new container untouched, nothing is lost at all.

Why was my file refused?

Because this browser could not decode what was inside it. That happens with older or unusual codecs, and it is better to hear so straight away than to receive a file with no picture in it.

Can it convert AVI or WMV?

No. Those containers are not read here. Anything a modern browser can play — MP4, MOV, WebM, MKV, MPEG-TS — is fair game.

Video Converter

Move a video between MP4, WebM, MKV and MOV.

Everything runs inside your browser. Your files never leave your device.

Drop your files here

.mp4, .m4v, .mov, .qt, .webm, .mkv, .ts, .mts, .m2ts · they stay on this device

Ask about Video Converter

Questions about what this tool does, which option to pick, or what it can and cannot handle.

This is the one part of the site that uses a server. The question you type here is sent to an AI provider to be answered — your files and whatever you put in the tool above are not, and the assistant cannot see them. Answers are generated and can be wrong; the tool itself is not guessing.

About the Video Converter

Format arguments between video files are really arguments about two separate things that get muddled together: the container, which is the box, and the codec, which is how the pictures inside it are written. A file called MP4 is a box that usually holds H.264 video and AAC audio. A WebM is a box that usually holds VP9 and Opus. Changing the box is cheap; changing what is in it is not.

This tool changes both when it has to and only what it must. MP4 is the default because it is the file that plays everywhere without a conversation — televisions, old phones, presentation software, the upload form that rejects everything else. WebM is offered beside it because its codecs are royalty-free and because a machine that cannot encode H.264 can nearly always encode VP9. MKV takes essentially anything, which makes it useful as an archive and useless as something to send to a colleague. MOV is what a Mac hands you and what several editing suites prefer to be given back.

The conversion runs on the codecs this browser already ships in order to play video. There is no separate media library to download first and no thirty-megabyte wait before the first click, and because everything happens in this tab, a confidential recording is never handed to a server that promises to delete it later.

The limit that follows from this is worth stating plainly rather than hiding: what can be read is what this browser can play. A file in an unusual codec will be refused with a message saying so, instead of appearing to work and producing something broken.

How to use it

1Add the videos you want converted.
2Choose the container you need. MP4 for sending to people, WebM for the web, MKV to keep, MOV for an editor.
3Set a quality — high is a sensible default and only matters when the codec has to change.
4Convert, then download.

Questions

Which format should I pick?: MP4, unless something specific told you otherwise. It is the only one you can send to a stranger and be confident it opens.
Does converting lose quality?: It does whenever the video has to be encoded again, which is most of the time. Where the existing frames can simply be moved into the new container untouched, nothing is lost at all.
Why was my file refused?: Because this browser could not decode what was inside it. That happens with older or unusual codecs, and it is better to hear so straight away than to receive a file with no picture in it.
Can it convert AVI or WMV?: No. Those containers are not read here. Anything a modern browser can play — MP4, MOV, WebM, MKV, MPEG-TS — is fair game.