Online Tool Store
Video Compressor
Shrink a video's file size using FFmpeg compiled to WebAssembly. Free, no sign-up — your video is compressed in your browser, never uploaded.
🔒 This tool runs entirely in your browser. Your files are never uploaded to a server.
Higher compression → smaller file, more quality loss.
Loading the sample video — choose your own file to replace it.
How it works
- Choose a video file and a compression level.
- Click Compress video — it's re-encoded to a smaller file size.
- Preview it right on the page, then download the compressed video.
How the compression works
This tool loads FFmpeg — compiled to WebAssembly so it can run inside your browser tab — and re-encodes the video stream with the H.264 codec at a chosen Constant Rate Factor (CRF), a quality target that lets the encoder spend more bits on complex frames and fewer on simple ones instead of forcing a fixed bitrate throughout:
ffmpeg -i input.mp4 -vcodec libx264 -crf 28 -preset veryfast -acodec aac -b:a 128k output.mp4
CRF is an inverse quality scale — a lower number means higher quality and a larger file, a higher number means more compression and a smaller file. The four presets in this tool (Light, Balanced, Strong, Maximum) map to CRF 24, 28, 32, and 36; the audio track is re-encoded separately to AAC at a fixed 128 kbps so it doesn't dominate the savings on already-small clips.
FAQ
Does my video get uploaded anywhere?
No. Compression runs entirely in your browser using ffmpeg.wasm, a WebAssembly build of FFmpeg — your video file never leaves your device or touches a server.
How much smaller will my video get?
It depends on the source video and the compression level you pick — a Light setting keeps quality close to the original with a modest size cut, while Maximum can shrink a file by 70% or more at the cost of visible quality loss, especially on fast motion or fine detail.
What video formats can I compress?
Any format your browser can hand off as a file — MP4, MOV, WebM, MKV, AVI, and more — since the conversion engine bundles its own demuxers rather than relying on the browser to decode the container. The compressed output is always saved as MP4.
Why does the first compression take a moment to start?
The first click loads a ~30MB WebAssembly compression engine, since it's only fetched when you actually use the tool, not on every page visit. Your browser caches it, so later compressions on this page start instantly.
Is there a video length or file size limit?
No hard limit is enforced, but everything runs on your device's own CPU and memory, so very large or very long videos may be slow or run out of memory on lower-powered devices. It works best for clips up to a few hundred MB.
Does this change my video's resolution or frame rate?
No — this tool only re-encodes the video at a lower bitrate to reduce file size; resolution and frame rate stay the same as the source.
How we compare
| Feature | Online Tool Store | CloudConvert | HandBrake |
|---|---|---|---|
| No file upload — runs in your browser | ✓ | ✗ | ✓ |
| No sign-up or install | ✓ | Free tier is upload-limited | ✗ (desktop app) |
| Preview the result before downloading | ✓ | ✓ | ✓ |
| One-click compression levels, no manual settings | ✓ | ✓ | Exposes full encoder settings |
HandBrake gives you more control once installed, and CloudConvert is convenient but means uploading your video to a third party. If you just want a smaller file without installing anything or sending your video anywhere, Video Compressor gets you there faster.