How to Blur Part of a Screenshot So It Cannot Be Undone
September 13, 2026
Most people blur a screenshot to be polite: hide a customer name before posting in Slack, hide a balance before sending to support. The blur is doing a real job, though, and a real job has a failure mode. A blur that is too gentle leaves enough for someone to read it back.
This is what to use, what to avoid, and how to do it in the browser in a few seconds.
Soft blur versus pixelation
A Gaussian blur averages pixels with their neighbours. Applied lightly to a short string of large text, it leaves a shape that can be matched against candidate strings -- which is how blurred numbers and usernames have been recovered from screenshots more than once.
Pixelation replaces each block of the region with a single colour. With blocks large relative to the text height, nothing about the letterforms survives. A solid rectangle is equally safe and uglier. Either is fine; a light blur is not.
What to blur
- Anything that identifies a person -- names, emails, avatars, initials in a circle.
- Anything that identifies an account -- IDs, invoice numbers, API keys, even partially.
- Amounts, when they are someone else’s.
- Your own tabs and bookmarks bar, which is why capturing the page area rather than the whole screen saves a lot of blurring.
Doing it in the browser
Press Screenshot in the Demorta bar, drag the area, and in the editor choose Blur and drag over each region. It pixelates with a block size scaled to the region, which is the destructive kind. Download the PNG; the original is never uploaded anywhere, so there is no unblurred copy sitting on a server. Try the free screenshot tool.
If you are recording a full product demo rather than one frame, the demo editor has the same blur for screenshot steps and a redact tool for HTML captures that removes the text from the markup itself.
Check before you send
Zoom in on the blurred region once. If you can still tell how many characters there were, make the blocks bigger or draw a solid box. Then check the edges of the crop -- the thing you blurred often appears again in a sidebar, a breadcrumb or a browser tab title.
Frequently asked questions
- Can a blurred screenshot be unblurred?
- A light Gaussian blur on short, large text sometimes can, by matching the blurred shape against candidate strings. Pixelation with large blocks, or a solid box, cannot -- the information is removed rather than smoothed.
- What is the safest way to hide text in a screenshot?
- A solid rectangle or coarse pixelation, applied to the image before it leaves your machine. Avoid annotating on a layer that can be removed, such as a shape in a document that still contains the original image underneath.
- Is there a free tool to blur part of a screenshot?
- Yes. Demorta’s browser screenshot tool has a pixelating blur, crops, and downloads a clean PNG on the free plan. The image stays in your browser rather than being uploaded.
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