How-to guide
The safest redaction happens before the shutter clicks. Blur the sensitive parts in the page first, then capture, so the finished image holds nothing but frosted pixels, with no original hiding underneath to move, undo, or reverse.
Updated August 2026
Quick answer
To redact a screenshot safely, remove the sensitive content before you capture the image, not after, and cover short predictable values with a solid shape rather than a blur. Editing a saved screenshot leaves the original inside the file: a black rectangle added in an editor can sit on its own layer, and in a PDF the text underneath stays selectable. Redacting in the live page first means those pixels never enter the file at all. Then match the treatment to the content: a heavy blur is fine for prose, faces and imagery, but anything drawn from a small set of possible values (a PIN, a short code, a date) should be cropped out or covered, because it can be brute-forced regardless of blur strength.
With Blurr that is: open the toolbar with Ctrl + Shift + YCmd + Shift + Y (Cmd + Shift + Y on Mac), blur every private element at full intensity, verify nothing readable remains, then capture with your normal OS tool.
The important part
The difference is where the original data ends up. Redact after capture and it may still be in the file; redact before, and it never enters the file at all.
Drop a black rectangle on an image in an editor and the original pixels can survive underneath, in a saved layer or as a movable object in a PDF. Flatten it wrong and the data is one click away from anyone who opens the file.
A light Gaussian blur or a coarse mosaic over small, predictable text (like a number or a short ID) can leave enough signal for software to reconstruct it. Redaction has to destroy the information, not merely soften it.
When you blur an element in the live page and then screenshot it, the capture only ever sees the blurred result. A strong, high-intensity blur applied before capture replaces the underlying pixels in the image. There is no separate original layer to move, undo, or reverse.
One honest caveat. Blurring in the page solves the hidden-original problem: there is no layer, no text object, and no movable box left in the file. It does not make the blur itself irreversible. A blur is a low-pass filter, so it attenuates detail rather than destroying it, and short predictable text can be recovered by rendering every candidate and matching. Blur prose and images freely. Crop or cover anything short and guessable.
The mechanism
Almost every guide on this topic asserts that blur "can sometimes be reconstructed" and then never explains how. The mechanism matters, because it tells you exactly when a blur is safe and when it is useless.
A Gaussian blur is a low-pass filter. Each output pixel is a weighted average of its neighbours, so the fine detail is spread across a wider area rather than deleted. The signal is still present, just heavily attenuated and mixed together. That is the fundamental difference between obfuscation and redaction, and it is why a solid fill sits in a different category from every blur setting.
Nobody runs your image through a magic deblur filter. They do something far more reliable: take the same font, at the same size, on the same background, render every plausible candidate string, apply the same blur or the same mosaic grid, and compare each result to your pixels. The closest match wins. This is how the published tools Depix (2020) and Bishop Fox's Unredacter (2022) defeat pixelated redactions, and the same logic applies to blur.
Brute force only works when there are few enough candidates to test. That single fact decides everything. A 4-digit PIN has 10,000 possibilities and will fall at any blur radius. A US phone number, a date of birth, a short order ID, or a dollar amount sit in an uncomfortable middle. A paragraph of free prose is effectively infinite and is genuinely safe behind a heavy blur. Ask how many things the hidden text could be, not how strong the blur looks.
The swirl effect once used to obscure faces is a reversible geometric transform: apply the inverse and the original returns. It was undone in real criminal investigations. Any effect that rearranges pixels rather than discarding them belongs in the same category.
Reference
Two independent failure modes, tracked separately: whether the mask itself can be undone, and whether the original survives elsewhere in the file.
| Method | Mask reversible? | Short, guessable text | Free prose & imagery | Why |
|---|---|---|---|---|
| Solid opaque fill | No | Safe | Safe | Destroys the pixels outright. The only visual redaction with no recovery path, provided the file is flattened. |
| Crop it out of frame | No | Safe | Safe | The data is never in the image. Strictly the safest option, and the right answer for short values. |
| Replace with fake data | No | Safe | Safe | Swap in a fixture value before capturing. Also the most readable option for documentation. |
| Heavy blur (20px+ on 12-16px text) | In principle | Not safe | Safe in practice | Fine for paragraphs, faces and imagery. Not for a PIN, a code, or anything from a small set of possible values. |
| Light blur / soft haze | Yes | Not safe | Not safe | Leaves word shapes, character counts and line lengths. Treat as decoration, not redaction. |
| Pixelation / mosaic | Yes | Not safe | Risky | Each block averages a known region, which is exactly what makes brute-force matching work. Defeated by published tools. |
| Swirl / twirl distortion | Yes | Not safe | Not safe | A deterministic, invertible transform. Reversed in real criminal investigations. |
| Black box drawn over live text | N/A | Depends | Depends | The mask is opaque, but in a PDF or a layered file the text object underneath survives and stays selectable. Flatten, then verify. |
Blurr applies a blur, so it sits in the "heavy blur" row: right for prose, faces, dashboards and imagery, and the wrong choice for a short guessable value. What it does add over an image editor is that no original layer is ever written to the file.
Step by step
Blur first, verify, then capture. The whole flow adds about a minute and removes the guesswork.
Before you capture anything, open Blurr with Ctrl + Shift + Y (Cmd + Shift + Y on Mac) and draw a box over (or click) every private detail inside the page: names, emails, account numbers, and API keys. Anything outside the page, such as the address bar or a notification, has to be cropped out of the shot instead, because no extension can paint over browser chrome.
Drag the intensity slider to maximum, a 20px blur. That is well past the 12px to 16px text most pages render. A light haze or a coarse pixelation leaves recoverable traces, and so does any blur over a short, guessable string: crop those out instead.
Zoom the page in, check the edge of each blur, and confirm no characters peek out around the mask. If anything is legible, resize the blur or push the intensity higher.
Capture with your native screenshot tool: Cmd + Shift + 4 on macOS, Windows + Shift + S on Windows, or Shift + Print Screen on Linux, which GNOME and KDE both map to a region capture. The saved image records only the blurred pixels; there is no hidden original layer behind them.
Open the screenshot at full size and scan it once more. What you see in the file is exactly what everyone else will see. No preview shortcuts, no trusting a scaled-down thumbnail.
Avoid these
Most screenshot leaks are not exotic: they come from small oversights. Run this checklist before anything with sensitive data leaves your machine.
Blurring too lightly: a soft haze that still hints at the shapes underneath. Push the intensity up until the content is genuinely gone.
Leaving the edges exposed, so a character or two peeks out around a too-small box. Resize the blur to fully cover the text.
Blurring a short, guessable value (a PIN, a 4-digit code, a date) instead of cropping it out. Strength does not help when the candidate list is small.
Forgetting the address bar, tab titles, desktop notifications, and autofill dropdowns that can appear in the frame.
Trusting a small preview instead of opening the finished file at full size before you send it.
Sharing the file straight out of a synced folder, so the unredacted original is already in the cloud.
Scope
You do not have to invent a list. Two widely used standards already enumerate what counts as identifying, and they work as a checklist well outside the industries that mandate them.
Names, emails, phone numbers, home and IP addresses, account numbers, and photographs. HIPAA’s Safe Harbor method lists 18 identifier types that must be stripped before health data counts as de-identified, and it is a useful checklist well outside healthcare.
API keys, tokens, session cookies, connection strings, recovery codes. Treat these as compromised the moment they appear in a shared image, and rotate rather than hope.
PCI DSS allows displaying at most the first six and last four digits of a card number. If your screenshot shows more than that, it needs redaction regardless of who you are sending it to.
Address bar, tab titles, bookmarks, notification toasts, autofill dropdowns, and the profile chip. None of these are part of the page, so no extension can blur them. Crop, or share a single tab instead.
Beyond the pixels
You can redact everything visible and still leak. These four are the ones that catch careful people, and none of them are fixed by a better blur.
Screenshots carry creation timestamps, display scale, and on some tools the source app or window title. A phone photo of a monitor carries EXIF, sometimes including GPS. Strip it: Preview’s inspector on macOS, "Remove Properties" on Windows, or exiftool -all= from a terminal.
"Screenshot 2026-07-24 at 09.41.12 acme-corp-invoice.png" names the customer before anyone opens it. Rename before you attach.
macOS saves to a Desktop that iCloud may sync, Windows to a OneDrive folder, and several capture tools upload the original to their own CDN to generate a share link before you have edited anything. Check where your tool writes first.
Some pipelines build thumbnails from the source file rather than your edited version. If you edited in place, confirm the preview updated too.
Before you send it
Thirty seconds of checking catches almost every real-world miss.
Zoom to 400% and read along every edge of every mask. Stray characters hide at the boundaries.
Select all on the page and copy. If redacted text lands in your clipboard, the mask is visual only.
Open the saved file at 100%, not a thumbnail. What is in the file is what your reader gets.
Screenshot your screenshot and look at that. It shows you the flattened result with no editor affordances.
Ask someone else to look before it goes anywhere public. Fresh eyes find what yours have stopped seeing.
Terminology
These get used interchangeably and they guarantee very different things.
Honest limits
Blurr redacts what is rendered in a web page. Four situations need something else, and reaching for a blur in any of them is a mistake.
Use a redaction tool that removes the text objects from the content stream, not one that draws a rectangle over them. Acrobat’s Redact and Preview’s redaction do this; drawing a shape does not.
You need an audit trail, consistent redaction codes, and defensible process. Use purpose-built discovery software.
Blurring a screenshot of records does nothing to the records. Anonymise or pseudonymise at the data layer.
A PIN, a 4-digit code, a date of birth. The candidate set is small enough to brute-force at any blur strength. Crop it out or cover it with a solid shape.
One more limit worth stating plainly: a blur is a visual layer. The text underneath is still in the page, still selectable, and still readable in DevTools. Blurr protects against eyes, cameras, and screen capture. It is not access control.
Automation
If you screenshot with real data all day, stop drawing the same blurs. Let Blurr catch them for you before every capture.
32 built-in presets frost emails, phone numbers, card numbers, IBANs, SSNs, API keys, and crypto wallets wherever they appear, so a stray value never sneaks into a capture.
Frost every image, video, avatar, and ad by category, and mask your tab titles and favicons with Tab Privacy, so nothing outside your content leaks into the frame either.
The blurs you draw stay on your device. Only your keyword and Auto-Blur rules sync to your account when you sign in for Pro. The screenshots you take never touch a server.
Keep exploring
Blur salaries, customer data and dashboards before you present on Zoom, Meet or Teams. Share a tab to hide the browser frame, and mask your other tab titles while you are at it.
Learn moreRedact names, emails and account numbers before you capture a screenshot for docs, tutorials, support tickets or bug reports.
Learn moreHide API keys, secrets, connection strings and customer records with one tap before you demo, pair, or file a bug. Presets built for exactly this.
Learn moreAuto-blur images, videos and ads, and hide your own name, email and address so you never dox yourself live on stream or in a tutorial recording.
Learn moreFAQ
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