What is CRF and what value should I use?

CRF (Constant Rate Factor) controls quality vs. file size. Lower CRF = higher quality, larger file. CRF 18 is visually lossless, CRF 23 is good quality, CRF 28 is a good balance for sharing, CRF 35+ is noticeable quality loss but very small files.

Is my video uploaded during compression?

No. ffmpeg.wasm runs entirely inside your browser. Your video is processed locally and never sent to any server.

Does it work on mobile?

Yes. Works on iPhone Safari and Android Chrome without installing any app.

How much will the file size be reduced?

Results vary by content. CRF 28 typically reduces file size by 30–60% compared to a high-bitrate original. Videos with lots of movement compress less than static scenes.

Will the audio quality be affected?

Audio is re-encoded to AAC at 128 kbps, which is transparent quality for most content. The CRF value only affects video quality.

Video Compressor

Reduce video file size with a CRF quality slider — no upload, no cloud processing.

100% client-side · no upload

Video file (MP4, WebM, MOV…)

Settings Quality (CRF) — 18 = best, 40 = smallest

Load a file to begin.

How to use

Select your video file. MP4 and WebM are best supported.
Set the CRF value. CRF 28 is a good starting point for sharing. Go higher (30–35) for a smaller file, lower (18–23) for better quality.
Click Compress video and wait. Compression re-encodes every frame — larger files take longer. Download the result.

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Frequently Asked Questions

What is CRF and what value should I use?: CRF (Constant Rate Factor) controls quality vs. file size. Lower CRF = higher quality, larger file. CRF 18 is visually lossless, CRF 23 is good quality, CRF 28 is a good balance for sharing, CRF 35+ is noticeable quality loss but very small files.
Is my video uploaded during compression?: No. ffmpeg.wasm runs entirely inside your browser. Your video is processed locally and never sent to any server.
Does it work on mobile?: Yes. Works on iPhone Safari and Android Chrome without installing any app.
How much will the file size be reduced?: Results vary by content. CRF 28 typically reduces file size by 30–60% compared to a high-bitrate original. Videos with lots of movement compress less than static scenes.
Will the audio quality be affected?: Audio is re-encoded to AAC at 128 kbps, which is transparent quality for most content. The CRF value only affects video quality.

Last updated: 2026-05-20 By jarvisbox