ALL VIDEO TOOLS23
Video to MP4
Convert Video to MP4 Online — Free, No Upload Required
Rewrap MOV, MKV, AVI or M4V as MP4 — usually without re-encoding a single frame.
About Video to MP4
MP4 is the container almost everything opens: phones, TVs, browsers, editors, and every upload form that rejects everything else. Most of the time the video inside your MOV, MKV, AVI or M4V is already H.264 — the exact codec MP4 wants — and the only thing standing between you and a working file is the wrapper around it. This tool reads the file's streams first, then rewraps them. When the codec fits MP4, the compressed video data is copied across byte for byte: nothing is decoded, nothing is re-encoded, and the run finishes in milliseconds rather than minutes. The picture you get out is the picture you put in. When the codec does not fit — an iPhone recording in H.265, say, or an older AVI codec MP4 has no tag for — the tool tells you before it runs and offers a conversion to H.264 as an explicit second choice, with the cost stated plainly: that path decodes and re-encodes every frame, so it is slow and it is lossy. FFmpeg compiled to WebAssembly does the work inside the tab; the file is never uploaded.
Questions
Is my video re-encoded?
Not on the normal path. The tool reads the file's streams first, and when the video codec is one MP4 can hold, the compressed data is copied into the new container byte for byte — nothing is decoded, so nothing is lost. Only if the codec does not fit MP4 are you offered a real conversion, and that choice is yours to make.
Which formats can I convert from?
MOV, MKV, AVI and M4V. WebM is handled separately by the WebM to MP4 tool, because WebM's VP8 and VP9 video has no MP4 equivalent to copy across — that one genuinely has to re-encode.
Why is a container swap so much faster than a converter?
Because it does almost no work. A conversion decodes every frame and encodes it again; a container swap unwraps the already-compressed stream and rewraps it. On our test clip the rewrap finished in about 12 milliseconds, running at several hundred times realtime.
What happens if my video is H.265?
You are told before anything runs. H.265 (HEVC) is legal inside an MP4, but an H.265 MP4 still fails to play in plenty of the places people are converting for, so quietly rewrapping it would hand you a file with the same problem and a different extension. Instead you get the choice of converting to H.264, which re-encodes every frame — slower, and lossy.
Is there a file size limit?
1.5 GB. That is the cap the code actually enforces: a stream copy has to hold its output in the browser tab, and a tab tops out under 2 GB in a single buffer. For anything longer, trim the clip first.
Is my file uploaded to a server?
No. Transmute processes everything locally in your browser using JavaScript and WebAssembly. Your files never leave your device — there is no server, no upload, no cloud processing.