No. ffmpeg.wasm runs inside your browser; videos never leave your device.

How do preset and CRF relate?

CRF is the visual quality target (lower = higher quality); preset decides how much CPU time goes into achieving that quality. medium is default; veryslow compresses most efficiently but is slow; ultrafast is quick but produces larger files.

What's the difference vs. video resize?

Resize lowers the resolution (fewer pixels). Compress keeps the resolution but lowers bitrate (same number of pixels, less precision). You can combine both.

Can I compress a video that's already H.264 / mp4?

Yes. A higher CRF (e.g. 28) shrinks it further. You can never improve on the original quality though.

Back to Video

Video compress — shrink size, tune CRF / preset / x264

Re-encode a video with libx264 at the chosen CRF to shrink the file size while keeping the resolution. Pick a preset to trade speed for compression. Output is mp4. Supports batch processing and a single ZIP download.

videocompress

How to use

Drop the videos to compress. Keep the resolution; set CRF (target quality, 18–28 typical) and preset (ultrafast–veryslow), then click Compress. ffmpeg.wasm re-encodes via libx264. Slower presets achieve smaller files at the same quality but take longer. Output is mp4.

FAQ

Are videos uploaded?: No. ffmpeg.wasm runs inside your browser; videos never leave your device.
How do preset and CRF relate?: CRF is the visual quality target (lower = higher quality); preset decides how much CPU time goes into achieving that quality. medium is default; veryslow compresses most efficiently but is slow; ultrafast is quick but produces larger files.
What's the difference vs. video resize?: Resize lowers the resolution (fewer pixels). Compress keeps the resolution but lowers bitrate (same number of pixels, less precision). You can combine both.
Can I compress a video that's already H.264 / mp4?: Yes. A higher CRF (e.g. 28) shrinks it further. You can never improve on the original quality though.

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