Convert video
MP4, WebM, and MOV, re-encoded in your browser.
This runs in your browser. Nothing is uploaded. Longer clips take longer here than they would on a fast server — that is the trade-off for not sending the file.
About Convert video
Converts a video to MP4, WebM, or MOV in your browser with FFmpeg compiled to WebAssembly, so the file is never uploaded.
Most “free online converters” take the clip, park it on a disk you do not control, and email you a link later. This page loads a local FFmpeg build once (about 30 MB, then cached) and does the work in a worker inside the tab. MP4 uses H.264 and AAC. WebM uses VP8 and Vorbis. MOV is the same family as MP4 when the source already is, and a remux (`-c copy`) is attempted before a full re-encode.
Re-encoding is slower than a rented GPU farm because it is your CPU. That is the point: a family video, a leaked-internal demo, a clip you would not drop on a random converter, stays on the machine. Long or 4K files will take minutes and can exhaust a tab around a gigabyte and a half — the UI warns before it tries to eat the whole file.
I am not chasing AVI, MKV, or FLV as first-class outputs. If the source is one of those, FFmpeg can often still read it and emit MP4 or WebM. If a remux fails, the page falls through to a real encode rather than handing you a broken container.
How to use Convert video
- 1Drop an MP4, WebM, MOV, or similar clip onto the panel.
- 2Wait for the encoder to finish loading the first time (about 30 MB).
- 3Pick MP4, WebM, or MOV, click Convert, then Download.
What it won't do
- No AVI/MKV/FLV as advertised outputs.
- Tab memory is the size cap, around 1.5 GB.
- The encoder is GPL FFmpeg compiled to WebAssembly.
Common questions
Does converting a video here upload it to a server?
No. After the page and the local encoder load from this origin, the bytes of your clip never leave the tab. Watch the network panel: you should see ffmpeg-core.wasm once, not a POST of the file.
Why is browser conversion slower than a website that ‘does it in the cloud’?
Those sites use someone else’s CPUs, which is also why they have your file. This page uses yours. A ten-second 480p clip is fine. A half-hour 4K dump belongs in HandBrake on the desktop.
Which formats can I convert between?
Outputs are MP4, WebM, and MOV. Inputs are whatever the bundled FFmpeg can demux — typically MP4, WebM, MOV, MKV, AVI. Exotic codecs still fail, and I will not pretend otherwise.
Related tools
Why this one doesn't upload your file
There is no server to upload to. This page is a static file, and the work happens in your browser using the same graphics and WebAssembly code that renders every other site you visit. Your file is read from disk into memory, processed, and handed back as a download. Once the page has loaded you can disconnect from the network entirely and it keeps working. The longer explanation