Product teams reach for blur because the screenshot still looks like the product. Attackers do not grade your aesthetic. They try contrast, invert, and leftover structure. A soft smear can leave digit stems. A black bar is a decision that those pixels get no future.
This page is the cover-policy decision guide for still screenshots: when blur or pixelate is enough for glance-level identity, when only an opaque bar is honest for a rotatable secret, and how to mix both in one frame without confusing the two jobs. It is not a device Markup cookbook. Phone and desktop capture recipes live on the linked device guides.
Open larger image in a new tabName the failure before you pick a cover
Redaction fails when the tool and the secret disagree. Ask one question first: are you hiding glance-level identity, or a secret you would rotate if it leaked?
Black bar is the default for short strings you would rotate: passwords, recovery codes, card digits, phone numbers, emails, session cookies, OTPs, and query tokens. An opaque rectangle removes glyph shape. A light smear keeps enough outline that someone can guess a digit from spacing alone.
Blur and Pixelate suit faces and messy backgrounds when “not identifiable at a glance” is enough. Pixelate is a different look, not a ranked upgrade at the same strength. Neither is a security guarantee for short digits, and neither is identity-proof against someone who already knows the person. If the string is a secret people can type from memory after one peek, use a bar.
What research says about leftover structure
Hill, Saorma, and Saul measured mosaicing and blurring over document text at PETS 2016. Their paper is about printed and scanned redaction habits, not a consumer “unblur” website. The operational lesson for a PNG is the same: leftover structure is leftover secret. Short strings with a small alphabet are the worst case. Six SMS digits, four digits of a card if the rest of the plastic is in frame, and a 2FA backup code in monospace all keep enough shape under a polite filter.
A heavy mosaic over a long paragraph can still be a poor choice if you needed deletion. A solid fill is simpler to audit: zoom in, look for peeking pixels, look for anti-aliased crumbs at the edge of the box. If you can still name the letter, the box is too small or too transparent. A short reader's note on that paper lives at PETS 2016.
Why blur looks more professional (and when that costs you)
Blur preserves the silhouette of the UI. Marketing decks, bug reports, and store reviews all want the reader to recognise the screen. A black slab says “we hid something,” and some teams hate that. Hide it anyway when the something is a token. You can keep the rest of the layout. You do not owe a stranger the glyphs.
Translucent highlighters are worse than a honest blur. A yellow tint in Markup or Snipping Tool often sits on top of the pixels. Raise brightness and brilliance and the words can return. That failure is documented in press coverage from 2018 onward, and on this site in the Markup brightness reveal. A filled shape at full opacity is closer to a bar. A translucent marker is not. For Windows capture limits after Win + Shift + S, see how to blur with Snipping Tool.
How to choose blur or black bar on one screenshot
Match the cover to the failure: glance-level faces can use heavy Blur or Pixelate. Rotatable secrets need Black bar. Export PNG and verify at full size.
In BlurThis
Open the screenshot blur tool. These steps are cover-policy only:
- Drop or paste the screenshot. Editing stays in this tab.
- For a face in a stand-up still, select Blur or Pixelate and Box. Pad past hair and ears. What you should see is a person you cannot name at a glance.
- For passwords, OTPs, cards, cookies, phones, and query tokens, select Black bar. Full opacity. Pad past descenders.
- Mix freely in one frame when both jobs appear. Download PNG. Open the export, not the editor. Zoom. Invert. Nudge brightness. The bar interior should stay empty. The face smear should stay unreadable at a glance.
Open larger image in a new tabWhat JPEG does to a cover you already applied
Chat apps recompress. Ringing around a light blur can outline glyphs. Start with PNG so you are not adding your own lossy pass on top of theirs. A hard black edge can ring too, but the interior of the bar stays empty. A light smear has interior structure that compression can emphasise. JPEG vs PNG for redacted screenshots covers the export choice in more depth.
Do not screenshot the editor window to “save” the result. That is a second resample. Use the download control. Do not flatten by sending through an app that turns PNG into a sticker with extra compression unless that is the only channel you have, and even then the source file should still be the barred PNG, not a JPEG of a blur.
Mixing blur and bars in one screenshot
Yes, mix them. Faces in a stand-up photo: blur if policy allows it. The Slack sidebar with customer email: bar. The URL with token=: bar the chrome. The notification that landed mid-capture: bar the banner or recapture. Mixing is not a contradiction. It is matching the tool to the failure you care about. Glance-level identity is not the same as a rotatable secret.
If you are unsure, bar. You can still describe the UI in the ticket text. You cannot un-send a PNG that still has a session cookie in the address bar. Credential-specific steps live in hide an API key before a bug report. Face-specific stills live in blur a face in a photo. The general stills walkthrough is how to blur a screenshot.
Device Markup without repeating every OS recipe
Built-in editors on phones and desktops can draw a filled rectangle that behaves like a bar when opacity is full. They can also tempt you into a highlighter tint that fails a brightness test. This page does not paste four OS Markup walkthroughs. Use the guide for the device you are on: iPhone, Android, Windows, Mac. Bring the same cover policy with you: bar for rotatable secrets, heavy blur only when glance-level identity is the goal.
If glyphs return when you invert
You used an overlay, a highlighter, or a mosaic with leftover cells. Paint a fill. Export again. Keep the original off the thread. Rotate anything that was ever visible on a file you posted, even if you think the bar covered it. Consumer unblur sites invent pixels and call it restoration. A solid bar gives them nothing to invent from. Unblur vs gone.
The rule that holds up
Blur or pixelate for glance-level faces, knowing neither is identity-proof. Bar for anything you would rotate. PNG export. Zoom and invert before you send. Both modes live in the same tab on BlurThis: drag a box, pick a heavy smear or a fill, download PNG.
