About this tool
This tool runs the genuine FFmpeg encoder — the same engine professional editors and YouTube's own pipeline are built around — compiled to WebAssembly so it runs entirely inside your browser tab. The first use downloads the engine once (about 32 MB); after that it is cached by your browser. Your video is processed on your device and is never uploaded to any server, which makes this safe for unreleased content.
Compression here means re-encoding with the H.264 CRF quality scale. CRF 23 keeps near-original quality, CRF 28 typically cuts file size by half or more with a small quality cost, and CRF 34+ is for previews and messaging apps where size matters more than detail. If your export is 4K and your audience watches on phones, capping height at 1080p or 720p saves more than any quality slider.
How to use it
- Choose your video file — it stays on your device.
- Pick a CRF: 23 for quality, 28 balanced, 34 for maximum shrink.
- Optionally cap the height (720p is plenty for most uploads).
- Press Compress, watch the progress, then play and download the result.
Tips from real creator workflows
- Compress a COPY — keep your master export untouched.
- For YouTube uploads, extreme compression backfires: YouTube re-encodes anyway, so feed it CRF 23–26 for the best final quality.
- Talking-head videos compress far better than fast-action gaming footage at the same CRF.
Frequently asked questions
Is my video uploaded to a server?
No. The FFmpeg engine runs in your browser via WebAssembly; the file never leaves your device. You can even go offline after the engine has loaded once.
Why is the first run slow to start?
The one-time engine download is about 32 MB. Your browser caches it, so later compressions start instantly.
What quality should I choose?
CRF 28 is the balanced default. Use 23 when the compressed file is your upload master, 32–36 for previews, drafts and WhatsApp-sized shares.
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