How to redact a screenshot so the covered data is actually gone.

A surprising share of "redacted" screenshots can be un-redacted. Marker strokes that looked solid turn out to be semi-transparent. Black boxes sit on a separate layer anyone can delete. Cropped-out edges linger inside the file itself. If the screenshot holds a password, an address or a client's name, that is a real problem.

This guide covers the four common ways redaction fails, then a procedure that works with any tool: destroy the pixels, flatten on export, verify by reopening. The worked example uses Arrowbox, because flattening is how it exports by design — but the checks apply to whatever you use.

Open Arrowbox — free, no sign-up

Runs in your browser. Nothing is uploaded — zero network calls, enforced by the page’s Content-Security-Policy. Desktop browsers work best.

How it works

Paste your screenshot into ArrowboxOpen arrowbox.app and press Ctrl+V to paste, or drag the file in. Nothing uploads — the page makes zero network calls after it loads, so the unredacted image stays on your machine.
Cover every secret with the Redaction toolPick Redaction and drag a box over each password, name or number. Choose solid black, pixelate or blur per box. Cover the whole string — one visible character narrows the guesswork.
Export a flattened copyPress Ctrl+S and export as PNG, JPEG or PDF. Arrowbox flattens on export: the pixels under every redaction are destroyed in the output file. No layer to delete, no original hiding underneath.
Verify on the export, not in the editorReopen the exported file in a different viewer and zoom in on each redaction. If you exported a PDF, press Ctrl+A and copy — pasted text exposes anything still live under a box.
Share the export onlyA saved .json project keeps the original pixels so you can re-edit later. Treat it like the unredacted original. The file that is safe to send is the exported PNG, JPEG or PDF.

Why most screenshot redaction fails

There are four distinct failure modes, and each has caught real people out.

See-through strokes. Marker and highlighter tools darken the image rather than replace it. A quick brightness and contrast pass in any photo editor brings the text straight back. It looked opaque on your screen; it wasn't.

Annotations on a separate layer. Some editors store your shapes as objects sitting beside the image, not burned into it. Open the file in the same app and the box lifts off. PDFs are the worst case: a black rectangle drawn over text leaves the text itself intact underneath — select all, copy, paste into a text editor, and it is all there. This is how badly redacted court filings keep ending up in the news.

The file keeps the old image. In March 2023, the "aCropalypse" disclosure showed that Google Pixel's Markup editor had spent years saving cropped and edited screenshots without truncating the original file — the "removed" data stayed inside the PNG and could be substantially reconstructed. Within days the same class of bug was confirmed in the Windows 11 Snipping Tool. The pixels looked right; the file container leaked anyway.

Weak obfuscation. Blur and pixelation reduce information; they do not remove it. Short strings in a known font and format can be brute-forced by generating candidates and matching the distortion.

The safe procedure, whatever tool you use

1. Redact with something opaque and destructive. Solid fill beats blur for anything critical.

2. Export to a flat image, or a PDF built from flattened pages. Flattening merges every layer into plain pixels.

3. Reopen the export in a different program and inspect each redaction. In a PDF, try to select text under the boxes.

4. Crop before you share. Data that is not in the file cannot be recovered from it.

5. Send the export. Keep the original, and any project file, private.

If your current editor passes those checks, keep using it. Many don't.

Where Arrowbox fits

Arrowbox flattens by design. Redaction is a built-in tool with three modes — solid black, pixelate, blur — and on export the pixels underneath are genuinely destroyed in the PNG, JPEG or PDF. There is no annotation layer in the output and no stale original in the file container. Because the app makes zero network calls after load, the unredacted screenshot never touches a server either — a quiet risk with most online redaction tools. Try it at [arrowbox.app/redact-screenshot](/redact-screenshot).

One caveat, stated plainly: a saved .json project keeps your originals so you can re-edit. Share exports, not projects.

Why Arrowbox

Redactions are destroyed on export — the output has no hidden layer, no undo, no original underneath
Runs entirely in your browser; zero network calls after load, so the unredacted screenshot never leaves your machine
Three modes per redaction: solid black, pixelate or blur
No account, no sign-up, no watermark — paste, cover, export
Works offline: save the page once and run it from a USB stick or an air-gapped machine
Free, donation-supported, one self-contained HTML file

Questions

Can a blurred or pixelated screenshot be recovered?

Sometimes. Light blur or coarse pixelation over short, predictable text — card numbers, number plates, passwords — can be reversed by rendering guesses through the same distortion and comparing. For anything critical use solid black, and always judge the exported file, not what the editor shows you.

Is putting a black box over text safe?

Only if the box is flattened into the pixels. Many editors, and almost all PDF tools, store the box as an annotation beside the image — it can be deleted, or the text beneath selected and copied. A flattened export leaves nothing under the box to find.

How do I make sure a redaction cannot be undone?

Reopen the export in a different viewer and zoom in on each redaction. In a PDF, select all and copy to check for live text. Then confirm you are sharing the export — project files, originals and cloud backups still contain the unredacted image.

Does Arrowbox upload my screenshot while I redact it?

No. Arrowbox makes zero network calls after the page loads — enforced by an automated build gate, not just a promise. There is no account and no telemetry. For sensitive work, save the page with Ctrl+S (HTML only) and run it fully offline.