Blur faces in a video

How it works

1. Add an MP4 or MOV video. The sound is copied across untouched.
2. Choose a blur, a mosaic or a black box, and how strong it should be.
3. Press Blur faces. The detector (about 0.2 MB) downloads the first time and is then already there.
4. Download the new MP4. Your original file is left exactly as it was.

Frequently asked questions

Does the cover follow a face as it moves?

Yes, and that is what this tool is for. Every frame is looked at separately, so a cover moves with the person rather than sitting where a box was drawn. A face the detector loses for a moment — turned away, in shadow, smeared by movement — keeps its cover for about half a second, and the cover widens while it is held, because the face is no longer where it was and nobody knows which way it went.

Which faces does it miss?

Faces small in the frame, in profile, in the dark, or covered by a hand or a mask. The detector looks at each frame shrunk to 640 pixels on its longer side, so a face that is a few pixels across in that copy is not found — although at that size it is not recognisable either. If nothing at all is found you are told so rather than handed back a file that looks finished. Watch the result before you publish it.

How long does it take?

About as long again as the clip itself: two seconds of a small video took two and a half seconds on the machine this was measured on, and an older one will take longer. Every frame is decoded, read by the detector and encoded once more, on a single thread. The video background remover, on the same clip and the same machine, takes eighteen seconds — because finding a face is a small question and separating a person from a room is a large one.

Does it cover licence plates too?

No. This detector was trained on faces and finds nothing else, so a number plate goes through untouched. For a plate, a name badge or a screen, use Blur part of a video, where you mark the areas yourself — that works when the thing you are hiding stays put.

Can I leave one face visible?

Not here: everyone found is covered, which is what makes it automatic. When you need to keep one person and hide the rest, mark the areas by hand with Blur part of a video instead.

Is my video uploaded?

No. The detector is fetched into your browser once and every frame is read on your own machine. That matters more for this tool than for almost any other on the site: the footage that needs anonymising is usually the footage you cannot hand to a stranger to do it for you.