Redact a screenshot before it leaves your phone

You took a screenshot of a chat with a seller, circled the line you didn't understand and sent it to the marketplace's support team with one question: what does this mean? Twenty seconds, done, forgotten.

Except more than that one line left your phone. The frame also carried the other person's name and profile picture, two other conversations in the list on the left and a notification that dropped down at the exact moment you pressed the buttons, with the first sentence of someone else's message in it. You didn't mean to send any of that.

Two things are worth pinning down before talking about how to hide anything. A screenshot copies the whole screen, not the part you were looking at. Your eyes crop; the screenshot doesn't. And covering something on the image removes it from the image, not from wherever it actually lives. Blacking out a phone number in a screenshot doesn't take that number out of the order, the group chat or your account on the other side. What you're doing is smaller than that, and still worth doing: you're stopping this one picture from carrying it any further.

So the real question isn't whether to cover things. Everyone knows you should. It's how, and how much.

Blur, pixelate, black box or remove: which one actually hides it

This is where most advice starts, and for good reason: the four common ways to hide text in a screenshot don't leave you with the same result.

Why blurred and pixelated text can come back

In a paper in the 2016 PoPETs Proceedings, a privacy research publication, Steven Hill of UC San Diego and three co-authors tested exactly this habit. The abstract opens with a scene anyone online will recognize: "In many online communities, it is the norm to redact names and other sensitive text from posted screenshots. Sometimes solid bars are used; sometimes a blur or other image transform is used." The researchers showed that they could use "a simple but powerful class of statistical models — so-called hidden Markov models (HMMs) — to recover both short and indefinitely long instances of redacted text." Their conclusion is blunt: "We conclude that mosaicing and blurring, despite their widespread usage, are not viable approaches for text redaction."

The security firm Bishop Fox made the same point with working software. Dan Petro, a security engineer there, wrote a tool called Unredacter "that takes redacted pixelized text and reverses it back into its unredacted form."

That doesn't mean anyone with a laptop can read back every blurred word. It means short strings with a predictable shape are the weak spot: a phone number, a ZIP code, an order number that always follows the same pattern. If the person receiving the image can guess the format, a blur leaves them something to work with.

A solid box: safe, and obviously redacted

Bishop Fox describes its own rule for reports as long-standing policy: "when you redact text, the only way to do it securely is to use black bars." The same article sums it up: "when you need to redact text, use black bars covering the whole text. Never use anything else. No pixelization, no blurring, no fuzzing, no swirling."

Two details separate a box that works from one that only looks like it does. Cover the whole string, edge to edge, in a fully opaque color. Then save the result as a new image file, so the box becomes part of the picture instead of a layer sitting on top of it. The same article warns about the document version of this mistake: black text on a black background in a word processor, which anyone can still read by highlighting it.

A box has one obvious side effect. Everyone who looks can see that something was hidden there.

Removing the text: seamless, with no box to show it was there

The third option takes the words away and fills the space with what's around them. Screenshots are the easy case for this, because app backgrounds tend to be flat and evenly colored, so the filled area usually blends in. Text sitting on top of a busy picture, like a caption printed over a photo inside the screenshot, is harder and worth a second look.

Done well, removal leaves no sign that anything was there. That's its strength, and in one situation it's also its problem.

Proof or illustration? Let the screenshot's job decide

These methods aren't interchangeable, because screenshots have different jobs.

If the screenshot is proof (a complaint, a dispute, something you may need to point to later), hide things in a way that shows they were hidden. The person receiving it should be able to see that a part was taken out and where. A seamless removal works against you here: the image looks complete, and when you later need to explain a missing line, there's nothing to point at.

If the screenshot is an illustration (a how-to, a post, a slide), the opposite holds. Nobody needs to know what used to be there, and a smudge or a black bar only makes the image uglier and pulls the reader's eye straight to the spot you wanted them to skip.

One question settles it: is this screenshot here to prove something, or to show something?

What to look for, layer by layer

Once you know how you'll hide things, the harder part is finding everything worth hiding. There are three layers, from the obvious to the easy to miss.

What anyone can read in three seconds

Names, faces, home addresses, phone numbers, profile pictures. USA.gov's page on identity theft lists the kinds of personal and financial information involved — "Names and addresses", "Credit card or Social Security numbers", "Bank account numbers" and "Medical insurance account numbers" — and its advice is direct: "Do not share personal information like your bank account number, Social Security number, or date of birth."

This layer is rarely where people slip, though. Everyone sees it, so everyone covers it. The real leaks sit where your eyes pass but your attention doesn't stop.

Numbers that point straight at you

The second layer looks harmless because none of it is a name. It's strings of letters and digits, and each one opens a different door.

• Order and tracking numbers. A tracking number identifies one specific package — yours — so treat it as an identifier and cover it.
• The address bar. It sits at the top edge and looks the same on every page, which is exactly why it gets missed. The end of a web address often carries an account, order or case number; some pages even put your username there.
• Card and account digits, along with the balance next to them in a banking app.
• Payment QR codes. A screenshot keeps every pixel sharp, so a code inside one usually still scans. Venmo's help page explains that "Your personal QR code is connected to your Venmo profile" and that "When you center the camera over the QR code, you'll be taken to that user's profile page". Its scanner reads saved pictures too: "If someone shared their QR code image with you, tap the photo icon at the bottom of the scanner page to use a saved image from your device." Nobody has to read the code to use it.
• File names and window titles. An attachment named after a contract and a person says three things at once: there is a contract, who it's with and that you're the one holding it.

The point of this layer fits in one sentence: these details rarely expose you to strangers; they expose you to someone who already knows half the story. On its own, a tracking number in a stranger's hands is just a string of characters. In the hands of someone who already knows your name or where you work, it can be the missing piece.

Sometimes the giveaway isn't text at all but something inside a photo that appears in the screenshot: a package by the front door with a label on it, a car in the background, a name badge. Those are objects, not words, and they call for a different tool. More on that below.

The edges you stopped seeing

The third layer is where most leaks happen, because it isn't part of what you meant to send. It sits around the edges.

• Notification banners are the costliest. A message from a third person drops down just as you take the screenshot, often with the sender's name and the first line showing. Now you've forwarded a piece of someone else's private conversation to a person neither of you knows, which is the hardest kind of mistake to apologize for. If banners are a risk for you, the fix lives in your phone's notification settings, where you can usually choose whether message previews appear.
• The chat list shows who you've been talking to (a work group, a family thread, a name nobody needed to know you're in touch with), often with the last line of each conversation.
• Browser tabs say what else you have open: where you're comparing prices, what you're reading, which record you were looking at. Shortened titles are still guessable.
• The account name in a corner of the app ties the image to one person in one system. It has been sitting there since the day you signed up, so nobody notices it anymore.
• The clock and battery pin the screenshot to an exact moment. That sounds harmless until the moment shows you were at your desk when you said you were somewhere else.
• The messages just above and below the part you meant to send. Crop tight, and the line above still slips into the frame. Sometimes it's the line where you talked about the very person who's about to receive it.

The cheapest fix here isn't a better memory. It's a different order of looking: check the four edges first, then work toward the middle. The middle is the part you've been staring at all along.

A yardstick borrowed from federal court filings

How much of a number is enough to hide? There's no law about screenshots, but there is a rule federal courts apply to documents people file, and it makes a useful yardstick. Under Federal Rule of Civil Procedure 5.2(a), unless the court orders otherwise, a filing that contains a Social Security number, a taxpayer-identification number, a birth date, a minor's name or a financial-account number may include only "(1) the last four digits of the social-security number and taxpayer-identification number; (2) the year of the individual's birth; (3) the minor's initials; and (4) the last four digits of the financial-account number."

This isn't legal advice, and the rule governs court filings, not screenshots. It's simply a fair benchmark: if a federal court keeps no more than the last four digits of an account number in a filing, a screenshot you send to a stranger has little reason to show more.

Removing text with Vipix: which tool does what

If you go the removal route, Vipix has two tools that do quite different jobs, and choosing the wrong one is the common mistake.

Remove text: every line it finds, in one press

Remove text is built for the one-press job: its one-press run clears every bit of text it detects and fills the background back in, with nothing for you to outline.

That makes it the right fit when none of the words should travel, for example when you want to show the layout of a screen without any of its content. It's the wrong fit for the usual case, where you want to keep the conversation and lose one line: in a single press, every line it finds goes.

Remove objects with Brush or Box: only the part you mark

When the job is to keep everything except one thing, use Remove objects. It works from a mask of the area to remove. In its Brush mode you paint over exactly that area, and the drawing tools also include Box, where you drag diagonally to frame a whole area, and Eraser, to take back a stroke. Its target is whatever you mark: one name in a chat header, a QR code, the label on the package by the door.

If what you need to clear is a watermark or a logo rather than ordinary text, the choice works differently, and which tool fits a watermark, plain text or an object walks through it.

Two things Vipix doesn't offer are a black-bar tool and a text-blurring tool. For a proof screenshot, use a solid shape in any photo editor (the markup tool built into your phone will do), then save it as a new image and check that copy.

When a run uses credits, you'll see the cost in the editor before you confirm.

Before you hit send: the exported file, its name and the copy you kept

The last step takes about thirty seconds and catches most of what slipped through.

• Open the saved copy, not the editor. Save the redacted version as a new file, then open that file in your photo viewer and zoom in on every spot you covered. The editing screen shows your edits layered on a preview; the file is what the other person will actually open.
• Look at the file name before you attach it. It travels with the image and can be read too.
• Think about where it's going. A group chat of twelve is not a private message, and in a group the image gets saved, searched and forwarded again.
• Remember the copy you didn't redact. The original screenshot is still in your camera roll, right next to the redacted one, taken a minute apart and nearly identical in the thumbnail grid. That's the one you're most likely to attach by mistake.
• Look at the corners of anything you download. Depending on the tool and on whether you were signed in when you ran it, a file you download from Vipix may have a small vipix.vn mark at its lower right, one more reason to open the exported copy before it goes anywhere.

One note about storage. Photos uploaded to Vipix and their results are kept for a limited time, and Vipix's Privacy Policy lists the exact periods. If a screenshot shows a Social Security number or a full account number, cover it on your own device before you upload it anywhere at all.

If your situation is the reverse, and you're sending photos to a client and want your mark to stay on them, that's a different problem, covered in watermarking proofs before you send them to clients. Text printed into an old photo, like the orange date in the corner of a film print, is a separate job too: see how to remove a date stamp from old photos.

Frequently asked questions

Is blurring enough to hide text in a screenshot?

Not for short strings such as phone numbers, account numbers or names. Researchers have recovered blurred and pixelated text with statistical models, and a security firm has published a tool that reverses pixelation. Use a solid, fully opaque box over the whole string instead.

Can someone unblur or unpixelate a screenshot?

Sometimes, yes. Published research and a public tool both do it, especially for short text with a predictable format. A solid box that covers the whole string, saved into a new image file, replaces those pixels outright, which is why it's the safer choice.

What personal information should I hide before sharing a screenshot?

Names, faces, addresses, phone numbers, Social Security numbers, bank and card numbers, order and tracking numbers, payment QR codes and anything in the address bar. Then check the edges: notification banners, the chat list, browser tabs, the account name and the clock.

Does removing text from a screenshot delete the information?

No. It removes the information from that image only. The order, the chat and the account it came from still hold it. Hiding it in the screenshot simply stops this one picture from carrying it further.

Will the edited screenshot carry a watermark?

It can, depending on which tool you used and on whether you were signed in when you ran it. When there is one, it's a small vipix.vn mark in a corner, so open the downloaded file and check before you send it.

Before you send the next one

Open the screenshot you were about to send and check its four edges first. If it's going out as an illustration, brush out what shouldn't travel with it in Remove objects, or, if every line of text has to go, run it through Remove text. If it's going out as proof, cover what matters with a solid box and send the new copy.