How to pixelate part of a photo on iPhone

Pixelation is the internet's shorthand for “this part is private”. It is also the method people most often get wrong — a light mosaic over text can be reversed. Here is how to do it properly.

Blur or blocks — which should you use?

They hide the same information, but they say different things.

• Blur looks softer and more natural. It suits faces, backgrounds and anything where you want the edit to blend into the photograph.
• Pixelation looks deliberate. It reads as "this was hidden on purpose", which is what you usually want for a screenshot, a document, a name badge or a licence plate — nobody should wonder whether it was an accident.

For anything resembling text or numbers, blocks also have a practical advantage: it is obvious at a glance whether the characters are still legible.

How to do it

1. Open the photo in an editor with a pixelate brush.
2. Pinch to zoom in on the area you are covering — precision matters more than speed.
3. Set the block size before you start painting, so you can see how coarse the result will be.
4. Paint over the area. Extend a little past the edges; a half-covered digit is still a readable digit.
5. Export a new copy and check it at full size.

In Blur Photo this is the Pixelate tool. Brush size and block size are separate sliders — brush size is how wide your stroke is, block size is how large each square becomes. An eraser undoes any stroke that went too far, and every stroke is covered by undo and redo.

The mistake that leaks data

Pixelation is not encryption. It averages each block of pixels down to a single colour — a lossy but mathematically predictable transformation. When the hidden content is drawn from a small, known set, such as digits, a licence plate format, or a font at a known size, it is possible to render every candidate, pixelate each one the same way, and see which matches. Researchers have demonstrated exactly this against pixelated and swirl-obscured text.

What actually protects you:

• Use large blocks. If the covered area is only a handful of blocks wide, there is not enough averaging to be safe. Increase the block size until the shape underneath is completely unreadable.
• Cover generously. Include the whole field, not just the characters — partial context narrows the search.
• For anything high-stakes, cover it solidly. Bank details, ID numbers, passwords, addresses: use a heavy blur or a solid block rather than a delicate mosaic. Losing that part of the picture is cheaper than losing the data.

Checking your work

Open the exported file and zoom all the way in. If you can guess a single character, so can someone motivated. Then check the rest of the frame: the same information often appears twice — a name on a badge and again on a screen, a plate on the car and again in a wing mirror.

Styles beyond plain blocks

Square blocks are the default because they are the clearest signal. Blur Photo also offers a mosaic style, which uses a hexagonal grid for a softer, more designed look on faces and backgrounds. It is a Premium style; the standard block pixelate is free.

Don't forget the file itself

Pixelating a house number does not help if the photo still carries the GPS coordinates where it was taken. Blur Photo removes location metadata from exported copies by default. There is more on that in the guide to hiding personal information.

Questions people ask