Video Converter — MP4, WebM, MOV, AVI Online, No Upload

Convert video formats without trusting a stranger's server

A video converter is one of the most-searched utilities on the web, and almost every result works by uploading your file to a cloud server. That's a strange default for personal recordings, work footage, or anything private. This converter runs the full FFmpeg engine in your browser via WebAssembly: pick a file, pick a format, and the transcoding happens on your own CPU with nothing transmitted anywhere.

MP4, WebM, MOV, AVI — when each one makes sense

MP4 with H.264 video and AAC audio is the universal donor — the right answer for sharing, uploading, and playback on unknown devices. WebM uses open, royalty-free codecs and embeds cleanly in web pages. MOV is the QuickTime container Apple tools prefer, and AVI keeps two decades of legacy Windows software happy. The container matters less than the codec inside it — which is why this tool re-encodes properly instead of just renaming the extension.

Built on FFmpeg — the engine everything else uses

FFmpeg is the open-source project that quietly powers most video software, from editing suites to streaming platforms. Running it as WebAssembly means you get the industry-standard decoder support (MKV, 3GP, camera formats, odd phone containers) without installing anything — and without granting any website custody of your files.

Part of a full on-device video toolkit

Need a smaller file rather than a different format? The video compressor handles that. Want just a section of the video, a GIF for chat, or only the audio track? Each tool runs on the same in-browser engine — download it once and the whole suite is instant for the rest of your session.

Frequently asked questions

Which format should I convert to?

MP4 (H.264) unless you have a specific reason otherwise — it plays on effectively every device, browser, and app made in the last fifteen years. WebM suits web embedding with open codecs, MOV fits Apple-centric workflows, and AVI exists mainly for legacy Windows software.

Are my files uploaded anywhere?

No. Conversion runs on a WebAssembly build of FFmpeg inside your browser. The only download is the engine itself (once, ~31 MB); your video is demuxed, re-encoded, and remuxed entirely on your own device.

What input formats does it accept?

Practically anything FFmpeg can read, which is nearly everything: MP4, MOV, WebM, AVI, MKV, 3GP, MTS, and most phone and camera formats. If a file fails, it's usually an unusual codec inside the container — try the High quality setting, which re-encodes rather than copies.

Does converting reduce quality?

Converting between lossy formats always re-encodes, which costs a small, usually invisible amount at the Standard setting (CRF 26). Choose High (CRF 20) when the output needs to survive further editing or another round of compression later.

Why does WebM take longer than MP4?

The VP8 encoder used for WebM is simply slower than x264 in a single-threaded WebAssembly environment. For long videos where you just need broad compatibility, MP4 is both the faster and the more portable choice.