Free · no signup · never uploaded
Video Compressor
Shrink a video to a smaller file — right in your browser, no upload, no watermark.
Drop a video here or choose a file
or drop your file here.
MP4 · MOV · MKV — compressed in your browser, never uploaded
Runs in your browser — your file is never uploaded.
Short answer
To compress a video, drop it below, choose a quality level and download the smaller file. It re-encodes with H.264 entirely in your browser — your video is never uploaded. Lower quality means a smaller file; “Balanced” is a good default.
Guides
How much smaller will my video get?
It depends far more on the source than on the setting. A video exported straight from a phone or a screen recorder usually has a lot of headroom and can drop by 50–80% at “Balanced” with no visible difference. A clip that was already compressed once will shrink much less, because the redundancy has already been squeezed out. Re-compressing an already-small file mostly just costs quality — if the size barely moves, that’s the signal to stop.
What do the quality levels actually change?
Each level sets a different CRF (constant rate factor), the knob H.264 uses to trade quality for size. “High” keeps the picture close to the original, “Balanced” is the sweet spot most people want, and “Smallest” pushes hardest and can show softness or blocking in detailed scenes. CRF targets a consistent quality rather than a fixed bitrate, so simple scenes get small automatically and busy ones keep the bits they need.
Video compression presets (H.264)
| Preset | CRF | Typical size vs original | Best for |
|---|---|---|---|
| High | 20 | 50–70% | Archiving, re-editing later |
| Balanced | 26 | 25–40% | Email, Slack, general sharing |
| Small | 32 | 10–20% | WhatsApp, slow connections |
CRF is H.264's constant-rate-factor quality scale — lower is better quality and a bigger file. Size reduction varies with the source: footage that is already heavily compressed shrinks less. Every preset uses the veryfast x264 preset because the browser build is single-threaded.
How the compression works
Everything happens locally in your browser with ffmpeg — here is exactly how:
- Load the engine. ffmpeg compiled to WebAssembly loads once from this site (self-hosted, not a third party) — your file is never uploaded.
- Check the input. the clip’s size and duration are read locally and checked against this tool’s limits before anything else happens, so an unworkable file is refused immediately.
- Re-encode with H.264. video is encoded with libx264 at the CRF matching your chosen quality, using the veryfast preset because only one thread is available; audio is re-encoded to AAC.
- Hand back the file. the MP4 is written with its moov atom moved to the front (+faststart) so it plays immediately, and handed over as a download.
Assumptions
- Everything runs client-side; speed depends on your device, the clip length, and its resolution.
- H.264 is lossy — compression cannot add back detail the source never had.
- Very large or long files are limited by your browser’s available memory.
Last reviewed: July 19, 2026
Frequently asked questions
How do I compress a video?+
Drop your video in above, choose a quality level, and download the result. The whole thing runs in your browser with ffmpeg, so your video is never uploaded. Lower quality settings produce smaller files.
Are my videos uploaded to a server?+
No. Everything runs 100% in your browser using ffmpeg compiled to WebAssembly, so your file never leaves your device. Nothing is uploaded, stored, or sent anywhere — and once the converter has loaded it even works offline.
Will compressing lose quality?+
Yes — H.264 compression is lossy, so some detail is always discarded. At the “High” and “Balanced” settings the loss is usually invisible at normal viewing size. “Smallest” trades visible sharpness for the biggest saving.
Why is there a file-size limit?+
Compression re-encodes every frame on a single thread inside your browser, which is far slower than a desktop app. The limit keeps the page from freezing on a file it realistically cannot finish.
Why is the first conversion slower?+
The first time, your browser downloads the ffmpeg engine (about 31 MB) and starts it up. That happens once — later conversions reuse the loaded engine and are much faster.
What format do I get back?+
An MP4 with H.264 video and AAC audio — the most widely compatible combination, playable on essentially any phone, browser, TV, or editor.
Related tools
Video is processed entirely in your browser with ffmpeg and never uploaded.