Blur or pixelate an image

No. The photo is decoded and edited on a canvas inside your browser tab, and the new file is written there too. That matters most for exactly the photos people blur: children, other people’s faces, ID cards, bank screenshots. You can load the page, turn off Wi-Fi and it still works.

Blur and pixelate are fine for faces, bodies and backgrounds. For text such as card numbers, addresses, names or passwords, use Black box. Research tools have recovered text from light pixelation and blur by trying likely words until the blurred result matches, and a solid box leaves nothing to recover.

Not from the file itself. The saved image contains only the blurred or pixelated pixels; the originals are not hidden underneath in a layer and the editing steps are not stored. Location and camera metadata are dropped too, because the file is written fresh from the canvas.

Yes. Press Find faces to have a face detector running in your browser mark them all, or drag a box over each one; every box gets the same effect. Tap the × on a box to remove it, or use Undo. Check the preview for any face the detector missed.

Choose "Whole image" and set the strength. Strength is relative to the size of the photo, so the same setting looks the same on a small screenshot and a 48 megapixel photo. At high strength pixelate gives the big-block mosaic look.

Yes. Choose Emoji as the effect, tap one of the common picks or type or paste any emoji, and every area gets it, sized to the box. The area is blurred underneath too, so nothing shows round the edges. The emoji is drawn in your device’s own emoji style, so it looks slightly different on an iPhone, Android or Windows PC.