Blur, Pixelate or Black Box: What Actually Hides Text in a Screenshot

Blur and pixelate hide text from a casual reader, not from someone who wants the secret; a solid black box is the only one of the three effects that removes the information. That difference matters the moment the screenshot holds a password, an account number or an address, because the effects look equally convincing and are not equally safe.

Disclosure: we build EditTextImage, which includes a browser-based blur tool with all three modes. The advice below applies whichever program you use.

What each effect actually does to the pixels

Blur spreads each pixel into its neighbours, so letters smear into a soft patch. Pixelate replaces each block of pixels with one averaged colour, so a line of text becomes a few flat squares. A black box replaces the selected pixels with solid black. The first two keep information about the original; the third does not.

That is the whole security story. Blur and pixelate are made to stop a person glancing at the screen. They are not made to stop someone who has the file and a reason to look harder.

Why pixelated text can be read again

Pixelation is a fixed averaging, so it is repeatable. If someone knows the font and what kind of text it was, such as a password or a phone number, they can render their own guesses, pixelate them the same way and compare. The open-source tool Depix recovered passwords from pixelated screenshots by doing this. A light blur can be partly reversed too.

Short, predictable strings are the weak spot: passwords, card numbers, account numbers and recovery codes. The fewer the possible characters, the easier the match. A long unique sentence is much harder to rebuild, but you should not rely on that for anything that matters.

Which effect to use for which job

• Passwords, card numbers, account numbers, recovery codes: a black box, or crop it out. Never blur or pixelate these.
• Names, email addresses, phone numbers, addresses: a black box if the screenshot is public; blur or pixelate is acceptable for a quick share with people you mostly trust.
• Faces, licence plates, logos: pixelate or blur works for appearance and privacy of bystanders. The goal there is usually to make them unidentifiable at a glance, not to defeat analysis.
• Text that is simply in the way: a blurred patch looks like a mistake on a product photo or a slide. Remove the text and rebuild the background instead; the text remover does that. For sensitive information, still prefer the black box, because it does not depend on how well anything was rebuilt.

Five places the same secret hides

Hiding the obvious value is half the job. Before you share a screenshot, check these:

• the browser tab title and the address bar, where IDs and tokens often sit
• notification banners that slid in while you took the shot
• the same value repeated further down the page or in a sidebar
• the phone status bar, with carrier, time and battery
• file details: a photo can carry GPS location in its metadata

A cover is not the same as an edit

Hiding text in a flattened image works because the pixels are gone. Drawing a black rectangle over text in a PDF or a slide is different: the words underneath often stay in the file and can be selected and copied. Export or screenshot the page as a flat image, then try to select text in the result. If you can select anything, it is not flat.

How to do it in a few seconds

Open the blur text in image tool, drag a box over each piece of text, choose Blur, Pixelate or Black box, and download. Draw the box a little larger than the text so the edges of the letters are covered. It runs in your browser, so the image is not uploaded, and it works on screenshots and photos including HEIC files from an iPhone. Zoom in on the result before you share it.

When not to use it: if you need the text gone so that the picture looks untouched, a blurred patch is the wrong tool, and if you need proof that something cannot be recovered, use a black box or crop and nothing else.

Frequently asked questions

Only edit images you own or have the right to change. Blurring is for protecting your own information, not for altering a record someone else relies on; see our acceptable use policy.