When to blur part of a photo
Before posting a photo from an event, blur the faces of people who didn't agree to be online — especially children. Blur number plates in car photos, house numbers and street names in photos of your home, and the name, address and order number in a screenshot of a delivery, a conversation or a bank transfer. Shops and property listings hide customers' faces and other people's cars; creators hide notifications and usernames in screen recordings.
A blurred background also has a softer use: it makes the subject stand out, or turns any photo into a calm backdrop for text.
Blur, pixelate or a solid box?
A strong blur is the natural choice for faces and backgrounds: it looks soft and nobody can recognise a well-blurred face. Pixelation is the classic TV look and is fine for faces too. For text — names, phone numbers, card or account numbers, addresses — use a solid box. Research has shown that small pixelated or lightly blurred text can sometimes be reconstructed by trying possible words until one looks the same; a solid box leaves nothing to reconstruct.
Turn the strength up rather than down: an area that's barely blurred can still be read.
Location and camera data
Phone photos carry hidden data (EXIF): the exact GPS position where they were taken, the date and time, and the phone model. Many apps remove it when you post, but not all of them, and files sent by email or messaging often keep it. The image you download here is redrawn from the pixels, so it carries none of that — handy even when you have nothing to blur.
Quality and size
The download keeps your photo's own size and aspect. JPEG photos are saved as high-quality JPEG; PNG screenshots stay PNG so text and interface edges stay sharp. Very large photos (above about 16 megapixels) are saved just under that size, the limit phones' browsers can draw.
Private by design
Your photo is opened and blurred by your own browser. Nothing is uploaded, stored or seen by anyone — which is the point when what you're hiding is private.