Pixelate an image

This mode opens with the whole picture pixelated. The Block size control sets how big each square is, and the line under it says what that means on your picture: the block edge in pixels, and roughly how many blocks fit across and down. Drag it low for a coarse, 8-bit look; high for something barely softened.

To pixelate only part of the picture, turn the whole-picture effect off and draw in Regions — Pixelate is the blur type it starts with on this page.

A mosaic keeps the shape of what it covers. It is a look, and a weaker covering than most people assume.

• In the Privacy mode a mosaic region reports how many blocks fit across its short side, and warns that the averages still hold structure.
• Saving — or Measure on a test copy — reads each region back out of the encoded file and prints the detail left inside a block.
• The solid fill is one press away in the same panel, and it is the only covering here that leaves nothing behind.

For a face that must not be recognised, use blur face in a photo with its solid fill. For a softer, lens-like look over the whole picture, use add blur to a photo. For text in a screenshot, redact the screenshot with hard bars.

• Pixelation is not a guarantee: large-scale structure survives in the block averages.
• An animated GIF or WebP is saved as its first frame.
• JPG, PNG, WebP, GIF, BMP and ICO open here. HEIC and TIFF open only where the browser itself reads them.

Is pixelation reversible?

Not exactly, but it is not a guarantee either. Each block is the average of the pixels it replaced, so the detail inside a block is gone — yet the pattern of blocks keeps the large shapes of what was there, and matching that pattern against candidate pictures or candidate text is a published attack. For something that must not be read, a solid fill leaves nothing.

What block size is safe for text?

No block size makes text safe in every case, which is why this site defaults to the solid fill for privacy. As a rule of thumb, blocks smaller than the height of a letter leave text readable, and short strings in a known format — plates, card numbers — can be recovered even from larger blocks. If it matters, fill it.

Can I pixelate only part of the picture?

Yes. Turn the whole-picture pixelation off, switch to Regions and draw over the part with a box, ellipse, brush or lasso; Pixelate is already selected as the blur type there. For faces, the Privacy mode shows how many blocks fit across each one.

Where do the block edges fall?

On a grid anchored to the picture's top-left corner rather than to wherever you started dragging, so the blocks sit square with the frame. In a region, the block size follows the region's own size, so a small region gets small blocks and a large one large blocks.