Pixelate Image

The image is divided into square blocks and every pixel in a block is replaced by the average colour of that block, so detail smaller than the block size disappears entirely.

Pixelation obscures detail but does not always destroy it: at small block sizes, text and faces can sometimes be recovered by software that tries many candidates and compares the pixelated result. For anything sensitive, use a large block size or a solid block instead.

The image censor tool applies pixelation, blur or a solid block to rectangles you drag over the picture, which is the right tool for hiding a face or a licence plate while leaving the rest sharp.

For a decorative mosaic, 8–20 pixels reads well on a typical photo; for hiding information, use a block large enough that the shape of what you are hiding is no longer recognisable.

The output keeps the original width and height — only the detail within it is replaced by blocks, so the file has the same dimensions but far less information.