How do I compress a video without uploading it?

Drop your file in, pick a preset (Balanced is a good default), and click Compress. The video is re-encoded entirely in your browser.

Is my video uploaded anywhere?

No. The compression runs locally using ffmpeg compiled to WebAssembly. The video never leaves your device.

What does CRF actually mean?

Constant Rate Factor — a quality dial for H.264. Lower numbers mean better quality and larger files: 18 is visually lossless, 22 is good, 26 is medium, 30 is small with visible compression. Each step of 6 roughly halves or doubles the file size.

How much can I expect a video to shrink?

Phone videos are often 5–10× smaller after compression at CRF 26. Already-compressed downloads might only shrink 20–40%. The size summary at the end of each run shows the exact ratio.

What's the maximum file size?

500 MB. WebAssembly's address space limits how much memory ffmpeg can use; 500 MB keeps headroom for the encoder.

Will the resolution be reduced?

Only if you turn on the advanced 'Max width' option. By default we keep the original resolution and just re-encode for size — capping width at 1280 or 720 is the easiest way to halve the file again.

What output container do I get?

Pick MP4 (H.264 video + AAC audio, `+faststart` enabled — the most universally playable format on phones, browsers, social media and editors) or WebM (VP9 video + Opus audio — open formats, typically ~20–30% smaller at the same visual quality, ideal for the web).

Why is compression slow?

WebAssembly runs single-threaded and is roughly 2–4× slower than native ffmpeg. A 1-minute 1080p video usually takes 2–4 minutes to compress in the browser; the trade-off is total privacy.

Does it work on mobile?

Yes, but slowly. Phones with under 4 GB of RAM may struggle on long clips — we show a soft warning when we detect low memory.

Is the video compressor free?

Yes — completely free, no signup, no watermark.

Video Compressor

Shrink MP4, MOV, WebM and MKV videos with H.264 + CRF presets, locally in your browser. The in-browser engine downloads once (~30 MB) on first use and is cached for the rest of your session.

Quick answer: Shrink MP4, MOV, WebM and MKV videos with H.264 + CRF presets, locally in your browser. The in-browser engine downloads once (~30 MB) on first use and is cached for the rest of your session.

Last updated 2026-05-01

Frequently asked questions

How do I compress a video without uploading it?: Drop your file in, pick a preset (Balanced is a good default), and click Compress. The video is re-encoded entirely in your browser.
Is my video uploaded anywhere?: No. The compression runs locally using ffmpeg compiled to WebAssembly. The video never leaves your device.
What does CRF actually mean?: Constant Rate Factor — a quality dial for H.264. Lower numbers mean better quality and larger files: 18 is visually lossless, 22 is good, 26 is medium, 30 is small with visible compression. Each step of 6 roughly halves or doubles the file size.
How much can I expect a video to shrink?: Phone videos are often 5–10× smaller after compression at CRF 26. Already-compressed downloads might only shrink 20–40%. The size summary at the end of each run shows the exact ratio.
What's the maximum file size?: 500 MB. WebAssembly's address space limits how much memory ffmpeg can use; 500 MB keeps headroom for the encoder.
Will the resolution be reduced?: Only if you turn on the advanced 'Max width' option. By default we keep the original resolution and just re-encode for size — capping width at 1280 or 720 is the easiest way to halve the file again.
What output container do I get?: Pick MP4 (H.264 video + AAC audio, `+faststart` enabled — the most universally playable format on phones, browsers, social media and editors) or WebM (VP9 video + Opus audio — open formats, typically ~20–30% smaller at the same visual quality, ideal for the web).
Why is compression slow?: WebAssembly runs single-threaded and is roughly 2–4× slower than native ffmpeg. A 1-minute 1080p video usually takes 2–4 minutes to compress in the browser; the trade-off is total privacy.
Does it work on mobile?: Yes, but slowly. Phones with under 4 GB of RAM may struggle on long clips — we show a soft warning when we detect low memory.
Is the video compressor free?: Yes — completely free, no signup, no watermark.