Video Compressor
Compress video files in your browser with FFmpeg.wasm. Adjust CRF quality, resolution scaling, and audio bitrate. Supports MP4 and WebM output. 100% local processing, no upload. Free online video compressor.
Drop a video here or click to browse
Supports MP4, WebM, AVI, MOV, MKV, FLV, WMV, 3GP โ recommended under 200MB
Frequently Asked Questions
Will compression reduce video quality?
Compression reduces bitrate to shrink file size, which does lower quality somewhat. Lower CRF values produce better quality but larger files. The recommended range of CRF 23-28 provides a good balance. For high quality, choose "High Quality" preset (CRF 18).
How do I get the smallest file size?
Choose "Small Size" preset (CRF 33) + scale to 720p or 480p + audio bitrate 64kbps for maximum compression. Quality will be noticeably reduced, suitable for chat sharing or web embedding where visual fidelity isn't critical.
Why is compression slow?
Compression speed depends on your CPU performance and video file size. Tips: 1) Close other CPU-intensive programs; 2) Compress smaller videos; 3) The first use downloads ~30MB of engine files which are cached afterward; 4) Lower resolution significantly speeds up compression.
What video formats are supported?
Input supports MP4, WebM, AVI, MOV, MKV, FLV, WMV, 3GP and other mainstream formats. Output supports MP4 (H.264) and WebM (VP8), which offer the best compatibility and compression efficiency.
What does CRF mean?
CRF (Constant Rate Factor) is a quality control parameter for H.264/VP8 encoders, ranging from 0-51. CRF 18 is visually lossless, CRF 23 is the default recommended value, and CRF 28 is acceptable quality with smaller files. Generally avoid going above CRF 35 as quality degrades noticeably.