Video Compressor — Reduce Video File Size Online
A video compressor reduces the file size of your videos so they're easier to share via email, messaging apps, or social media, and take less storage space. Our free online compressor uses FFmpeg (compiled to WebAssembly) to compress videos entirely in your browser.
Unlike tools that upload your videos to remote servers, this compressor runs 100% in your browser. Your videos are never uploaded, stored, or transmitted anywhere. This makes it completely private and secure.
Choose from quality presets (Low, Medium, High), set a target resolution, or use the advanced CRF control for precise compression. The tool supports MP4, WebM, AVI, MOV, MKV, and FLV input formats.
How to Compress a Video
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Upload your video Drag and drop a video file onto the upload area, or click to browse. We support MP4, WebM, AVI, MOV, MKV, and FLV.
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Choose settings Select an output format (MP4 or WebM), pick a quality preset, set a target resolution, or use advanced CRF settings.
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Compress Click "Compress Video" and watch the progress bar. The video engine loads automatically on first use (cached for future visits).
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Download Review the before/after comparison and click "Download" to save your compressed video.
Frequently Asked Questions
No, never. All video compression happens entirely in your browser using FFmpeg compiled to WebAssembly. Your videos are never uploaded, stored, or transmitted anywhere — making this tool completely private and secure.
The first time you use the tool, it downloads the FFmpeg WebAssembly engine (~30MB). This is cached by your browser, so subsequent uses are much faster. Video compression is also CPU-intensive — larger videos take longer to process.
Quality presets (Low, Medium, High) are easy-to-use settings that balance file size and quality automatically. CRF (Constant Rate Factor) is an advanced setting where lower values mean better quality but larger files. CRF 18 is visually lossless, 23 is default, and 28+ produces much smaller files.
MP4 (H.264) is the most widely compatible format — it works on virtually all devices and platforms. WebM (VP8) is a modern open format that produces smaller files but may not play on older devices. When in doubt, choose MP4.
There's no hard limit, but very large videos (several GB) may consume a lot of memory and take a long time to compress. For best results, keep videos under 2GB. Mobile devices may struggle with very large files.
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