Blur Faces in Videos

Once frames are changed they have to be encoded again. This tool writes VP9 or AV1 inside WebM, both free to use in a browser, and deliberately never produces a new H.264/AAC MP4. Most browsers, messengers and editors play WebM directly.

Each face is followed from frame to frame instead of being detected anew every time. A track that has been confirmed keeps running for a moment even while the detector loses the face, so a head turning to the side stays covered instead of flashing open for a few frames.

Reads MP4, MOV, M4V, WebM and 6 more formats. As many files at once as you like.

You get WebM.

Every frame is decoded and encoded again. That is what makes the file smaller or different — and it costs some detail, most visibly in fast motion and fine texture.

The first run downloads a small model to your device. After that it works offline. Which video codecs work depends on your browser. Chrome and Edge read the most, including H.265 on many machines; Safari and Firefox refuse some. A file that will not open here usually opens in Chrome.

Only when it has to be re-encoded. Cutting, joining and removing the sound track copy the picture data unchanged, so those are lossless. Compressing and adding a watermark do re-encode, which is why they take longer.

There is no fixed limit. What decides is the memory of your device: a phone manages a few minutes comfortably, a computer handles far more. If a long video fails, splitting it first and working on the parts usually helps.