Why video files are so much larger than photos
A video is, at its core, a rapid sequence of still images. 24 to 60 of them per second, depending on the format. A two-minute clip at 30 frames per second contains 3,600 individual frames, which is why even a short video can dwarf an entire folder of photos in file size. Modern video compression doesn't store every frame independently; it mostly stores the differences between frames, so a mostly-static scene compresses far better than fast, chaotic motion where nearly everything changes frame to frame.
How to compress a video with this tool
- Upload your video file.
- Adjust the quality setting (CRF). Lower values mean higher quality and larger files, higher values mean smaller files with more visible compression artifacts.
- Click Run to start compression. This uses ffmpeg running entirely inside your browser via WebAssembly, so processing happens locally rather than uploading your video to a server.
- Once complete, preview the result and download it.
Because this runs client-side rather than on a server, the first use in a session downloads the compression engine (a one-time download of roughly 30MB), and processing speed depends on your device's own performance rather than server capacity.
Choosing a compression level
For casual sharing (messaging, social media, quick previews) a more aggressive compression setting is usually fine, since these platforms often re-compress the video again on their end anyway. For anything meant to be archived, edited further, or viewed on a large screen, staying closer to a higher-quality setting preserves more detail, especially in fast-motion scenes and scenes with fine texture like grass, water, or fabric, which tend to show compression artifacts first.
There's no single correct setting, the right balance depends entirely on where the video is going and how critically it'll be viewed.
Practical limits of browser-based video processing
Because there's no server doing the heavy lifting, very large or very long video files can be slow to process, and extremely large files may run into your browser's available memory limits. This is an inherent tradeoff of processing entirely on-device rather than uploading to a remote server with dedicated processing power. The benefit is that your video never leaves your device, but the cost is that performance depends on your own hardware.
For most everyday clips (a few minutes long, moderate resolution) this isn't a practical concern. It becomes more relevant for very long recordings or high-resolution 4K footage, where a dedicated desktop video editing tool with hardware acceleration may process faster.