TopSecret documentation

Black out anything sensitive in an image or PDF — draw the bars yourself or let TopSecret find emails, IDs, card numbers, and faces for you. Export a flattened copy where the hidden data is genuinely gone, not just covered. Everything runs on your Mac. This page walks through how it works.

Installation

TopSecret comes two ways. The download from bendansby.com/apps/topsecret is a notarized .dmg — open it and drag TopSecret.app to your Applications folder. It ships with a free 7-day trial; a one-time license then unlocks unlimited use. The Mac App Store version is a paid-through-Apple copy that installs and updates the usual way.

Requires macOS 13 Ventura or later, on Apple Silicon or Intel. The direct-download build keeps itself up to date via Sparkle; you can also check anytime from within the app. The Mac App Store build updates through its own channel.

Opening an image or PDF

Drop a file onto TopSecret to get started — a screenshot, a photo, or a multi-page PDF. Whatever you hand it opens on the canvas, ready to redact. TopSecret only ever touches the file you give it.

TopSecret works entirely on your Mac. There is no network access, no account to create, and no telemetry — the file you open never leaves your machine.

Redaction is permanent

This is the whole point of TopSecret, so it's worth stating plainly: a redaction bar is not a sticker laid on top of your image. When you export, the bars are burned into a new flattened file and the pixels underneath are recomputed. The hidden text or face can't be selected, copied, or recovered from the exported copy — it's genuinely gone.

Exported PDFs are rasterized during this same flattening, so nothing lingers on a layer or in a text stream underneath the bar. What you see in the finished file is all there is.

Because flattening is one-way, always keep your original if you might need the un-redacted content later. The exported copy is meant to be safe to share precisely because the hidden data can't be brought back from it.

Redaction styles

Every bar can be rendered in one of three styles. Pick whichever suits the document:

Style	Looks like
Black bar	The classic solid blackout.
White bar	A solid white block — handy on dark or photo backgrounds.
Noise scramble	A random-noise fill that reads clearly as "scrambled on purpose" — a good look for faces in a photo.

Whichever style you choose, the result after export is the same underneath: the original pixels are recomputed away, not merely covered.

Drawing & adjusting bars

Drag on the canvas to place a redaction bar over anything you want hidden. Once it's down you can move it or resize it to get the coverage exactly right.

Drag out a bar to cover a region.
Move or resize a placed bar until it frames the sensitive area.
⌫ removes the selected bar.
Full named undo & redo covers every change, so you can back out of a mistake without starting over.

Auto-detect sensitive content

Rather than hunt for every sensitive field by eye, let TopSecret find it. One click scans the document and blacks out the things that most often need hiding:

Email addresses
Social Security numbers
Phone numbers
Card numbers
IP addresses
Faces

You can run detection on the current page or across every page. It all runs on-device with Apple's Vision framework — nothing is uploaded to find these things. Detected regions become ordinary redaction bars, so you can nudge, resize, or remove any of them before exporting.

Find & redact by text

When you know the exact word or number to hide, redact by text: TopSecret blacks out every occurrence of that string across the document in one pass. Turn on the optional fuzzy match to also catch close spellings and OCR slips, so a name or ID that got scanned imperfectly still gets covered everywhere it appears.

Images & multi-page PDFs

TopSecret handles single images and long PDFs alike. For a multi-page document, a thumbnail sidebar tracks the redactions on each page, so you can see at a glance where you've been and what's still bare.

You can also sweep the whole document in a single pass — run auto-detection or a text redaction across every page at once instead of stepping through them by hand. As with any export, PDFs are rasterized on the way out so nothing survives underneath the bars.

Exporting a flattened copy

When the document is redacted the way you want it, export it. This is the step that burns the bars in and produces the safe-to-share copy described in Redaction is permanent — a new flattened file with the hidden pixels recomputed away and (for PDFs) the pages rasterized.

Export produces a fresh file — your original is left as-is. Share the exported copy; keep the original somewhere safe if you may still need the un-redacted content.

Saving a session

Redaction bars stay editable while you work. Save your progress as a .topsecret session and you can reopen it later to move bars around, add more, or change styles — the flattening only happens when you export. That means you can rough out a redaction, come back to it, and refine it before committing to the final flattened copy.

Privacy

TopSecret is private by design. There is no network access, no account, and no telemetry — it only ever touches the file you hand it, and everything, including auto-detection, runs locally on your Mac. It's built in SwiftUI as a universal binary and, on the direct-download build, keeps itself up to date via Sparkle.

For the full details, see the privacy policy.

Support

Questions, bug reports, or feature requests? Email ben.dansby@gmail.com and you'll get a reply, usually within a day or two.