Question 1

What video formats are supported?

Accepted Answer

The compressor accepts MP4, MOV, AVI, MKV, and WebM files up to 500MB. Output is always MP4 (H.264 + AAC).

Question 2

What does CRF mean?

Accepted Answer

CRF (Constant Rate Factor) controls quality. Lower values mean better quality but larger files. 18 is visually lossless, 28 is a good default, and 32+ produces smaller files with visible quality loss.

Question 3

Why is processing slow?

Accepted Answer

Video compression runs in your browser using WebAssembly, so it's slower than native apps. We use the ultrafast preset by default for quicker encoding; choose a lower resolution for even faster results.

Question 4

Is my video uploaded to a server?

Accepted Answer

No. FFmpeg runs locally in your browser via WebAssembly. Your video never leaves your device.

Question 5

Why doesn't this work in my browser?

Accepted Answer

This tool requires SharedArrayBuffer and WebAssembly support. It works best in Chrome, Edge, or Firefox. Safari on iOS 16.4+ is also supported. Make sure cross-origin isolation headers are enabled.

Video Compressor

How to Use

Upload a video

Choose quality settings

Download compressed video

Frequently Asked Questions — Video Compressor

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