When and Why to Blur Part of an Image
Most blurring is done for one of two reasons: to hide something, or to push a background out of the way so the subject stands out. The Image Blur Tool applies an adjustable blur, and the amount you choose matters more than people expect.
Blurring to hide something
Screenshots are the usual case. An email address, an account number, a name in a sidebar, a password manager entry - things that have no business being in a picture you are about to publish. Faces and number plates in street photographs are the other common one.
Here is the part that catches people out. A light blur is reversible. Blurring is a mathematical operation, and if too little information has been destroyed, the original can be estimated back out of it. Short strings from a known set - a six digit code, a car registration, a dollar amount - are especially vulnerable, because software can try every possibility, blur each one, and see which matches.
So if you are hiding something that matters, blur heavily enough that nothing of the shape remains, or do not blur at all. A solid block of colour over the text is the only genuinely irreversible option, and for anything sensitive it is the right one. It looks less elegant and it cannot be undone, which is the whole point.
Blurring for effect
The other use is composition. A blurred background separates the subject from a cluttered room and mimics what a camera with a wide aperture would have done. A gentle blur reads as depth; a heavy one reads as a mistake, so less is usually more.
A blurred image also makes a reasonable background for text, since a soft field gives letters something to sit on without competing. If the subject is what you want and the background is the problem, removing it entirely with the Background Remover is often cleaner than blurring it.
Check what else the file is carrying
A photograph can reveal where it was taken without showing anything in the frame, because the location may be written into its metadata. Blurring the picture does nothing about that. The EXIF Data Viewer and Remover shows what is in the file and strips it.
Common questions
How much blur is enough to be safe?
Enough that you cannot tell there was ever text there. If you can see the rhythm of the words, it is not enough. For anything that matters, cover it instead.
Can blurred text really be recovered?
Light blurring of short predictable strings, yes - it has been demonstrated repeatedly. Heavy blurring of long arbitrary text is far harder, but why rely on it.
Does blurring the whole image help privacy?
Not usefully. It ruins the picture and still may not defeat recovery of a small region.
Is my image uploaded?
No. The blur is applied in your browser and the file never leaves your device.
Need to hide something in a picture?