How to Hide Faces and Private Details in Photos Properly

Sometimes you want to share a photo or a screenshot but not everything in it: a face, a number plate, an address or an account number. There are three ways to hide something, and they aren't equally safe.

Black box

A solid box replaces the pixels with a flat color. Nothing underneath is left in the file, so nothing can be recovered. Use it for anything you really must keep private: passwords, card numbers, account details, addresses and names on documents.

Blur

A blur mixes the pixels together so you can't make out the detail. It looks natural, and it's good for faces and number plates in the background. A light blur can sometimes be partly undone by software, so make it strong.

Pixelate

Pixelating turns an area into big blocks. It's recognizable and quick, but it has the same weakness as blur. Researchers have shown that short pieces of text and some faces can be guessed from pixel blocks, especially when the blocks are small.

A mistake that catches people out

• Putting a colored shape over the area in an editing program, and then saving it in a format with layers. The shape can be moved and the original is still underneath.
• Cropping instead of hiding, in a program that keeps the cropped area in the file.
• Forgetting the rest of the picture: reflections, a street sign, a letter on a desk, a face in a mirror.

The Blur & Censor tool changes the pixels in the saved file itself. There's no layer to remove afterwards.

Check the file as well

A photo can still give away where it was taken through hidden data, even when the face is hidden. Saving it from the censor tool drops that data, and the EXIF Viewer & Remover lets you check any file.

Ask first

If other people are in your picture, think about asking before you post it, even if they're hard to recognize. Hiding a face is courteous, but some people can be identified by their clothes, tattoos or the place.