What is video compression suitable for?
Video compression reduces the storage and transfer size of local video files. The tool runs ffmpeg.wasm in a Web Worker so long transcodes do not block the main interface; Comlink handles communication between the page and the Worker. Input files are not uploaded to The Browser AI servers.
Compression results are exported as MP4 and previewed with HLS.js or the browser's native HLS support. The resulting size depends on video duration, original bitrate, frame changes, compression strength, and target resolution; lowering the resolution usually reduces the size further. FFmpeg Core is downloaded on first use, and processing speed depends on your device.
Supported formats: MP4, MOV, WebM, AVI; single file limit: 500MB.
How to use video compression
Step 1
Select video
Upload a MP4, MOV, WebM, AVI or other browser-readable video that is no larger than 500MB.
Step 2
Set compression strength
Select compression strength and maximum resolution, then start compression; first run will download FFmpeg Core.
Step 3
Preview and download
Switch between the pre- and post-compression versions in the same player, confirm the size and image quality, and then download MP4.
FAQ
Will video compression reduce image quality?
Usually yes. Increasing the compression strength or lowering the resolution will reduce file size, but may reduce sharpness. It is recommended to adjust it file by file according to the purpose, and switch to preview for comparison before downloading.
Why does it take so long to compress the first video?
The first run requires downloading and caching FFmpeg Core from CDN, and then completing the transcoding on this machine. Download speed, video length, and device performance all affect how long it takes.
Will the video be uploaded to the server?
No. Video data is processed in a separate Worker in the browser; network requests are used to download the FFmpeg Core required for the program to run, rather than uploading the user's video.
Why are compressed files not necessarily smaller?
If the original video has been encoded with a lower bit rate or high efficiency, it may not be able to continue to be reduced when transcoded again. At this point you can increase the compression strength or choose a lower maximum resolution.
Technology and data sources
- ffmpeg.wasm — Official FFmpeg project documentation for running FFmpeg in the browser.
- Comlink — Open-source RPC library for communication between the page and a Web Worker.
- HLS.js — Used to play HLS previews in browsers with MSE support.