Video Format Converter

How to use Video Format Converter

1. Choose your video file.
2. Pick the target format — MP4 unless you have a reason not to.
3. Convert, and wait; the progress bar reflects real work rather than a guess.
4. Download the result.
5. Conversion happens in your browser — the file is never uploaded anywhere.
6. Expect minutes, not seconds: WebAssembly FFmpeg cannot use your machine’s hardware encoder.
7. Large files may exhaust browser memory; trim before converting where you can.

Container and codec are different things

MP4, WebM and MKV are containers — wrappers holding a video stream, an audio stream and metadata. H.264, VP9 and AAC are codecs, the actual compression. A file can be an MP4 containing H.264 video and AAC audio, or an MP4 containing something a given device cannot decode. That is why a “converted to MP4” file sometimes still will not play: the container changed and the codec inside it did not match what the player supports. This tool sets both — MP4 and MOV get H.264 and AAC, WebM gets VP8 and Vorbis.

Why it is slow, and when to use something else

FFmpeg here runs as WebAssembly in a browser tab, single-threaded, without access to the hardware video encoder your machine has. Re-encoding is computationally expensive, so expect minutes rather than seconds, and expect a long clip to be impractical. The trade is explicit: for a short clip that you would rather not upload — anything personal, confidential or not yet released — waiting is worth it. For a feature-length file, install FFmpeg or HandBrake and use the hardware.

Every conversion is a generation loss

Converting between lossy formats decodes and re-encodes, so quality drops each time, even at a nominally high setting. Convert from the highest-quality source you have rather than from something already converted, and convert once rather than experimenting through several formats. If all you need is a different container with the same streams inside, remuxing copies them without re-encoding and is both instant and lossless — a different operation from what happens here.

Which format to target

MP4 with H.264 is the safe answer: it plays on essentially everything, including old phones, smart TVs and embedded players. WebM with VP9 compresses better at the same quality and is well supported in browsers but poorly outside them. MOV is an Apple container, mostly the same content as MP4. AVI and MKV are legacy and enthusiast choices respectively. If you do not have a specific reason, choose MP4.