Video Compressor
Compress videos in your browser. No upload needed.
Drag & drop your video here
or click to browse
Supports MP4, WebM, MOV (max 500 MB)
Your video is processed entirely in your browser. Nothing is uploaded to any server.
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How to use Video Compressor
1
Drag and drop a video or click to browse. Supported formats: MP4, WebM, MOV.
2
Choose a quality preset (Low, Medium, or High) and optionally set a maximum resolution.
3
Click "Compress Video" to start processing. The video engine will download on first use (this may take a moment).
4
Once done, view the size reduction percentage and download the compressed video.
How it works
This video compressor uses FFmpeg compiled to WebAssembly (WASM) to process videos entirely in your browser:
- Loading: On first use, the FFmpeg WASM engine is downloaded and cached in your browser. Subsequent uses are much faster.
- Compression: The video is encoded using H.264 (libx264) with a CRF (Constant Rate Factor) value that controls quality. Lower CRF = higher quality but larger file. Audio is re-encoded as AAC at 128 kbps.
- Resolution: Optionally, you can limit the output resolution (e.g., 1080p, 720p) to further reduce file size. The aspect ratio is preserved automatically.
- Smart Check: If the compressed video is not smaller than the original, the tool keeps the original and informs you that the video is already optimized.
- Privacy: Your video never leaves your device. All processing is done locally using WebAssembly. No data is uploaded to any server.
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Frequently Asked Questions
Is my video uploaded to a server?
No. Your video is processed entirely in your browser using FFmpeg compiled to WebAssembly. It is never uploaded, transmitted, or stored on any server. Your privacy is fully protected.
What video formats are supported?
You can compress MP4, WebM, and MOV videos. The output is always MP4 (H.264 + AAC), which offers the best compatibility across all devices and platforms.
Why does it take time on first use?
The FFmpeg WebAssembly engine (~30 MB) needs to be downloaded on first use. It is cached in your browser afterwards, so subsequent compressions start much faster.
What does CRF mean?
CRF (Constant Rate Factor) controls video quality. Lower values mean higher quality but larger files. The presets map to: Low = CRF 28 (smallest file), Medium = CRF 23 (balanced), High = CRF 18 (best quality).
My browser shows a SharedArrayBuffer error. What do I do?
FFmpeg WASM requires SharedArrayBuffer, which is available in modern browsers (Chrome, Edge, Firefox) when served with proper security headers (Cross-Origin-Opener-Policy and Cross-Origin-Embedder-Policy). If you see this error, try a different browser or ensure you are accessing the site over HTTPS.
Is there a file size limit?
There is no hard limit, but very large or long videos will take longer to process and use more memory. Since everything runs in your browser, performance depends on your device. For best results, try videos under 500 MB.