slicerflowMedia toolsVideo compressor
🗜️ Runs on your device · nothing uploaded

Free video compressor
that runs in your browser

Drop a video and shrink it with an adjustable quality. FFmpeg runs on your own device (compiled to WebAssembly), so your file is never uploaded. Export a smaller H.264 MP4 — free, no account, no watermark.

No account · no install · nothing uploaded · MIT open source

# compress a video in 4 steps
1. Drop a video    mp4 · mov · webm · mkv
2. Set quality     CRF · lower = better
3. Run             FFmpeg on-device
4. Download        smaller H.264 MP4

Opens the 🎬 Video tab → Compress Video. Runs locally via FFmpeg (single-thread).

How to compress a video

From a big clip to a smaller file in four steps — no upload, no watermark, no sign-up.

Drop your video

Choose or drag an MP4, MOV, WebM or MKV. It loads into a private in-browser workspace — your file never leaves the device.

Set the quality

Pick a CRF — 23 keeps high quality, 28 balances, 34 makes small files — and a speed/size preset.

Run FFmpeg

FFmpeg (WebAssembly) re-encodes to H.264 right in the tab, showing progress as it goes.

Download

Compare the result and download the smaller MP4. Nothing was uploaded.

Why slicerflow's video compressor

More media tools

Video compressor — FAQ

How do I compress a video for free?

Open the tool, drop a video, set the quality (CRF — higher means smaller) and click Run. FFmpeg re-encodes it in your browser and you download the smaller file — free, no account.

Is my video uploaded?

No. FFmpeg is compiled to WebAssembly and runs entirely on your device, so the video never leaves your browser.

How small can it get?

It depends on the CRF you choose — around 23 keeps high quality, 28 is a good balance, and 34 makes small files. A speed/size preset trades encode time for compression.

Which formats are supported?

MP4, MOV, WebM and MKV inputs; the compressor outputs H.264 MP4. The Video tab also converts between formats and extracts audio.

Is it slow?

Because it runs on your own device (single-thread FFmpeg), large files take longer than a server would. A faster preset or trimming the clip first helps.

Shrink your video without uploading it

FFmpeg on your device, adjustable quality — free and private, in your browser.