Convert an MKV into an MP4 that plays almost anywhere

Open the tool, choose or drop your .mkv file, and it rebuilds the video as MP4 with the H.264 codec. When the file is ready, save the MP4. It all happens in your browser, so there is no upload step and no account to create.

Yes. The converter is free to use, with no sign-up, no trial, and no watermark on the file.

No. The conversion runs on your device with WebCodecs, so the file never leaves your browser and nothing is stored on a server.

Both are containers that hold a video and audio track. MKV (Matroska) is flexible and common for recordings and downloads, but many phones, browsers, and editors will not open it. MP4 is the format almost everything plays, which is why converting helps.

You keep the original resolution and frame rate. The video is re-encoded to H.264, so a single frame paused and zoomed in can look a little softer than the source. In motion the clip looks the same.

There is no fixed limit, because nothing is uploaded. A Matroska file can be several GB, and since the work happens on your own device, the practical ceiling is your computer's memory rather than a server allowance. Typical files convert fine; a very large one can be slower or bound by your device. On Chrome and Edge, big files can write the MP4 straight to disk as the tool works, so the whole output does not have to sit in memory.

Because the file is never uploaded, there is no transfer step: you choose the .mkv, it converts locally, and you save the MP4. For a quick result, leave the format on MP4 and the quality on Balanced.

Yes. The tool runs in your phone browser, so it works on iPhone and Android with no app to install. A phone has less memory than a computer, so a very large MKV is better converted on a desktop.

MP4 is the default because it has the widest support, but the same tool can also output WebM, MOV, or MKV if you need one of those. You can also remove the audio track or strip metadata before converting.