Video Compressor
Shrink MP4, WebM & MOV files with quality presets and resolution caps — compressed on your own device. Nothing uploads.
The page works offline. Your first compression downloads a one-time video engine (~25 MB) from a public CDN — after that it runs entirely on your device. The video itself is never uploaded.
or click to browse — MP4, WebM, MOV, MKV, AVI & more
⚠ Large file. Videos over 300 MB can exhaust browser memory — the engine runs in WebAssembly with a roughly 2 GB ceiling, and Safari is stricter still. It may work, but if the tab crashes try a shorter clip, a smaller file, or desktop Chrome / Edge / Firefox.
Source
—Balanced (CRF 28) — noticeably smaller with minor quality loss. Good default.
Honest expectation: in-browser compression usually runs at 0.3–1× video speed — a 2-minute clip can take 2–6 minutes depending on your device. Output is MP4 (H.264, web-ready, fast-start).
Result
—The output ended up larger than the input — it was probably already heavily compressed. Try the Strong preset or a lower resolution cap.
This browser can’t run the video engine
The in-browser engine needs WebAssembly and modern JavaScript modules. Try the latest Chrome, Edge, or Firefox on a desktop.
Why compress video in the browser?
Most "free" video compressors upload your footage to a server — slow, and your private clips end up on someone else’s machine. HeroTools runs a WebAssembly build of FFmpeg directly in your browser, so the whole job happens locally and the file never leaves your device. The trade-off is speed: a server farm is faster than your laptop, so long videos take a while. For big batches or very large files (300 MB+, especially on Safari), a desktop app is still the better tool — this one is for quick, private, no-install jobs.