How do you redact private information in an iPhone screenshot?

Why blur is not redaction

Blur and pixelation smudge an image, but they can leave clues. Someone can render likely values, apply the same effect and compare the results. Familiar layouts, repeated values and a short list of possibilities make that easier. A 2016 peer-reviewed study showed this against both mosaicing and blurring. Bishop Fox published Unredacter, a tool that recovers pixelated text by exactly this guess-and-compare method.

Recovery works only some of the time. The point is simpler: a solid cover in a flattened image leaves nothing of the original text in those pixels.

The real danger is that a blurred account number looks handled. Nobody checks it again, and the file gets sent.

What actually works

A solid cover, then flatten. A fully opaque rectangle, drawn into the pixels of the file you send. The information is destroyed, rather than hidden.

Three details catch people out:

• Make the box bigger than the text. Letters and their soft edges spill past the obvious outline. A box that stops at the last pixel can leave enough shape to read.
• Flatten before sharing. An editor that keeps shapes on a separate layer has only drawn on top of the original. Export a flattened copy and send that.
• Check the file you actually send, rather than the editor’s preview. Open the exported file, zoom to 100 percent, and try to select text.

The free way: Markup on iPhone or iPad

For one or two pictures, the built-in Markup tool is enough. It can draw a solid box (Apple’s Markup guide):

1. Open the screenshot in Photos, tap Edit, then open Markup. Right after taking a screenshot, you can also tap its thumbnail.
2. In the Markup toolbar, tap +, then Add Shape, and choose the square.
3. Use the toolbar options to give the shape a solid fill colour at full opacity.
4. Drag and resize the box so it covers the detail with room to spare. Repeat for every private detail, then tap Done.
5. Share the picture as usual. If you use AirDrop, open Options in the share sheet and leave All Photos Data off.

The steps are the same on iPad. With Apple Pencil, you can swipe up from either bottom corner to take a screenshot and mark it up straight away (Apple), and placing the box precisely is easier with the Pencil than with a finger.

Step 5 matters because Photos edits can be undone. Photos keeps your original so you can revert, and Apple’s sharing guide says All Photos Data sends “the original file with edit history”, so the recipient can change it (Apple).

Markup works well for a single picture. It gets slow when the same account number appears on twelve screenshots, and nothing checks what you missed. That is where a tool that reads every picture helps.

What people miss on an app screenshot

Everyone remembers the obvious fields. These are the ones that slip through:

• The status bar: carrier name and, on some devices, a personal hotspot indicator.
• A notification banner that dropped in mid-capture.
• Autofill suggestions above the keyboard, drawn from your own data.
• A tab bar badge count, which can reveal an internal figure.
• Links in a share sheet, which often carry account identifiers.
• QR codes and barcodes, which are machine-readable even at low resolution.
• Charts, where a balance you covered in text may still be plotted.

How Walkthru does it

Walkthru redacts with a drag-a-box tool. Each box is filled solid and drawn into every export. Blur and pixelation are left out on purpose: the exported file should hold the covered result, whatever app opens it.

It works on the screenshots you already have. Import them, accept the redactions, export. A recording is optional, and nothing is uploaded, because there is no server.

It reads each screenshot on the device and offers covers. It looks for email addresses, phone numbers, postal addresses, card numbers, IBANs, US Social Security numbers, ABA routing numbers, crypto wallet addresses, and strings that look like secrets: masked password fields, known API-key prefixes and random-looking tokens. For most values with a checksum, it checks the checksum instead of just the shape: Luhn and IIN for cards, mod-97 for IBANs, the FedACH check for routing numbers, Base58Check and bech32 for Bitcoin-style addresses. Ethereum-style addresses are matched by shape. Fewer false alarms means you keep reading the offers.

It offers; it never applies on its own. Offers appear as dashed outlines, with a card on the step. Redact accepts that step’s offers and Ignore dismisses them. To keep only some, tap Redact, then delete the boxes you don’t need. Nothing reaches an export until you accept it. Walkthru decides what is worth asking about; you decide what is private.

It asks before the riskiest details leave. If you share while a card number, IBAN, Social Security number, routing number, wallet address or likely secret is still unresolved, Walkthru asks first, for example “Share with a card number still visible?”, with Share Anyway or Review.

It can repeat a cover across steps. When the same detail sits in the same place on every screen, such as an account number in a header, Apply to all steps copies the box to the other action steps. It copies the position, not the meaning, so check that each copy still covers the right thing.

What you still check yourself

Detection is a helper, rather than a full privacy check. Walkthru skips personal names, so inspect names, balances, faces, QR codes and notifications yourself. Only the offers you accept become covers.

Review each picture in passes:

1. Identity: names, contact details, profile pictures and addresses.
2. Access and identifiers: passwords, codes, tokens, links, QR codes and references.
3. Context: balances, purchases, notes and notifications the audience can do without.
4. Repeats: headers, dialogs and later screenshots that show the same detail again.

Use sample data where you can. If a field must stay visible for the instructions to make sense, capture it with a sample value. A label such as Email address still helps the reader when its contents are covered.

In a video reel, a redacted step holds still on its covered screenshot. Because the picture stays still, a secret has no way to scroll out from under the cover.

The editable guide keeps your original screenshots, and your Photos library and backups keep their own copies. Send the exported file, never the originals or the source recording.

Check the exact file you send

Output	What to check
Image (PNG, JPEG or HEIC)	Open it and inspect the edges of every cover at full size. Look for the same detail elsewhere in the picture.
PDF	Check every page, including the written steps. Search or select any text that might hold the value.
Markdown bundle	Check the pictures and the written step text; an instruction can repeat a value you covered.
Video	Watch and listen to the whole file. A cover on the picture does not remove a secret spoken in the narration.

Failing to select text does not prove a file is safe; visible pixels can still be read. And covering a picture does nothing about text you typed into an instruction. Check both.

If the screen changes later

Recheck every cover after you replace a screenshot. A saved box may now sit beside the private value instead of on top of it. Apply to all steps copies positions; it does not follow an email address that moved when the keyboard opened.

Use the guide update checklist for replacements.