Online Video Compressor

About Online Video Compressor

A video that's too large to email, too slow to upload, or eating up storage space usually needs re-encoding at a lower bitrate to shrink down — but that traditionally means installing dedicated software or trusting a conversion website with the file. This tool runs a genuine FFmpeg build compiled to WebAssembly directly in your browser, compressing the video entirely on your own device.

Compression is controlled through a single quality slider using H.264's CRF (Constant Rate Factor) setting — a lower CRF value produces higher quality and a larger file, a higher CRF value produces a smaller file at reduced visual quality. This is the same approach professional video encoders use, since CRF adapts the bitrate per-scene based on complexity rather than forcing a single flat bitrate across the whole video.

The encode uses FFmpeg's "veryfast" preset, trading a small amount of compression efficiency for meaningfully faster processing — a reasonable trade-off for a browser-based tool where encoding speed directly affects how long you wait, especially on longer videos.

Before and after file sizes are shown once compression finishes, so you can immediately see how much was saved and decide whether to try a different quality setting for a better balance.

How it works

1. Upload your video. The file loads into the browser-based FFmpeg engine.
2. Choose a compression level. Slide toward higher quality or smaller file size.
3. Compress and download. See the before/after size and save the smaller file.