Lucerna
The Lucerna icon: a page, half white, half black.

Lucerna

PDF Night Reader

The page goes dark.
The photographs stay themselves.

Every PDF reader can invert a page. What none of them do well is invert only the parts that should be inverted — so the diagrams survive, but every photograph comes back as a negative. Faces in X-ray. Skies in orange. Plates of food no one would eat.

Lucerna reads the page's content stream, finds where the images actually sit, and leaves them alone.

Download on the Mac App Store

On macOS now. iPhone and iPad to follow shortly — and one purchase will cover all three.

Last security remediation:
Lucerna on a Mac: a library of sample books on the left, and a darkened spread on the right whose diagram is still printed the right way round.

What it does

A reader for people who read at night, for hours.

Narrower than a general-purpose document viewer, on purpose. Everything here exists because of something that happens on the fourth hour of reading, not the first minute.

Three modes, one shortcut

Black & White drains the colour from everything left — the quietest a page can be. Colour on Dark keeps it. Sepia gives back warm paper and quiet type. ⌘B moves between them.

A folder is a library

Point Lucerna at a folder and it finds every PDF underneath it, subfolders included, each drawn as its own first page. Sorting works the way the Finder's does.

It remembers where you were

Rotation, zoom, layout, and your exact place — page and scroll position — kept per document. Written as you read, so a force quit costs you nothing.

Bookmarks, and marks

⌘D keeps the whole page. ⇧⌘M marks the sentence you selected. They are different things and Lucerna keeps them apart, in a panel that lists both.

Stuck pages

Pin a contents page, a table or a plate to the head of the thumbnail strip, where it stays however far into the book you scroll. ⇧⌘T.

Pages, arranged

One page, two, two with the title standing alone, three across, or a grid of eight. Fit width, fit height, or a zoom of your own — and arrow keys that move by whatever is on screen.

Reflow, on iPhone and iPad

Real paragraphs rebuilt from the text layer: hyphenated words rejoined, paragraphs carried across page breaks, running headers dropped, type sized between 12 and 44 pt by pinching.

Handoff

Start a book on the Mac and the phone offers it at the same page. For documents kept in iCloud Drive, reading positions and bookmarks follow you too.

New files, noticed

Drop a document into a folder Lucerna is showing and it appears — no re-scan, no reopening anything.

On screen

A Mac window, a library, and a page.

Separate windows for the library and for each document — not tabs — and all of them come back where they were the next time you open the app.

The library, a folder of PDFs drawn as covers, beside an open document.
A folder of documents, each drawn as its own first page.
A page with a marked passage in amber, and a panel listing bookmarks and marks.
Marked passages and bookmarked pages, listed together.
A long page of text with page thumbnails down the left side.
Thumbnails drawn from the reader's own pages, so they invert with it.

In the store

What the listing shows.

The five pictures on the Mac App Store page, exactly as they appear there — the reader doing the five things it was built to do. The iPhone and iPad version is on its way, and one purchase will cover all three.

A darkened page whose drawings are still printed the right way round, under the words: the page goes dark, the drawings stay themselves. A folder of PDFs drawn as covers beside an open book, under the words: a folder is a library. A long page of text with thumbnails down one side, under the words: built for reading for hours. A passage being marked from the menu the system already puts beside a selection, under the words: mark it where you are reading. A line ruled in gold beside a paragraph, with rules and marked passages listed together, under the words: rule a line in gold.

And on the phone and the iPad.

The same reader, laid out for the screen it is on. These are the pictures from the iPhone and iPad listing, which is with Apple for review now.

Lucerna on an iPad: the library in a sidebar beside an open picture book. An iPad page with a bookmarks panel open down the right-hand side. An iPad showing page thumbnails beside a darkened page of a picture book.
Lucerna on an iPhone: a folder of PDFs drawn as covers. An iPhone showing a darkened page whose chart is still printed the right way round. An iPhone showing the same document reflowed into one readable column of text.

Why it exists

I wrote it for the way I read.

This is not here to replace the PDF readers that already do their job well. There are several, they are good, and most of them are trying to serve everybody. Lucerna came out of something narrower: my own scientific background, and a habit I picked up at university and never lost.

What I always needed was a way to glance at a PDF fast — to see what is in a paper before deciding whether it deserves an hour — and then a way to actually read, at night, for a long time, without the page burning a hole in the dark. Everything in the app is shaped around those two things and the four motions between them: see the library, add to it, read, switch to the next one — without losing where you were in the last.

It is an Apple-only app, and that belongs to the same story. Apple is a campus company. In the United States you feel it — in the lecture halls, in the libraries, in what people carry into a seminar. From outside the country you half believe it; you only really know it once you have lived there. The reading I am describing happens on those machines, so that is where the app lives.

That is the whole of it. A working method from the lab and the reading room, made into a tool I use every day. It is a scientific approach by origin, but nothing in it is only for academics: if you read at night, it is the same app.

— Alex

Paying for it

One payment. Not a subscription.

This app opens a file and darkens it. There is no server behind it, nothing that costs money to keep running, and so nothing honest to charge rent for.

Free for fourteen days

Whole and unhindered: no nag, no watermark, no page limit. After that, one payment unlocks reading for good.

  • Bought once for the Mac — and for the iPhone and iPad when they arrive
  • A lifetime unlock, not a yearly one
  • Your own recents, bookmarks and marks are never locked
Download on the Mac App Store

What it never does

The claims here are the app's entitlements, not a promise.

  • Never modifies your PDFs — inversion is a drawing pass, nothing is written back
  • Sandboxed, with read-only access to the files you choose
  • No account, no server, no analytics, nothing sent anywhere

Requirements

macOS today. iPhone and iPad shortly.

Lucerna is on the Mac App Store now and needs macOS 15 or later. The iPhone and iPad version — iOS and iPadOS 17 or later — is with Apple for review, and follows as soon as it clears. One App Store listing carries all three, so whichever you buy first unlocks the others when they land, at no further cost. Apple's Preview gained a dark-mode toggle in macOS Tahoe and it is good — but it is a general-purpose document viewer: no library, no memory of where you were, no reading modes. Lucerna is narrower than that, on purpose.

Security

No known vulnerabilities.

What ships, what it is built from, and what is known to be wrong with it — published in line with the EU Cyber Resilience Act and brought up to date with every release scan. The numbers below are from the scan of 11 October 2026.

No known vulnerabilities · scan of

Nothing known to be exploitable in any shipped component, and nothing open in the tooling that builds this site either.

Components scanned3
Packages covered4532 shipped · 13 build-time
Open, in shipped code0
Open, in build-time tooling0
Fixed, 10–11 October 2026101 critical · 4 high · 3 moderate · 2 low — all in build-time tooling
ComponentVersionPackagesOpenStatus
Lucerna for Mac
Mac App Store · sandboxed, hardened runtime · Apple frameworks only		 1.0.2 0 0 No known vulnerabilities
Lucerna for iPhone and iPad
App Store, in review · Apple frameworks only		 1.0 0 0 No known vulnerabilities
This site and its two endpoints
Static files behind CloudFront; the support form and AI Lookup on AWS Lambda		 — 45
32 shipped · 13 build-time		 0 No known vulnerabilities

“Shipped” packages run as part of the product; “build-time” packages only build or test it and never reach you. The Mac and iOS apps are built on Apple's system frameworks alone and carry no third-party code. Per-package detail and the bills of materials are not published; they are available to customers, partners and market-surveillance authorities on request, through the contact below.

Reporting a vulnerability

Write to info@sp33c.tech, which is also named in security.txt. Reports are acknowledged within five working days. A fixed vulnerability shows in the counts here once the update is out; the details go to the reporter, and to customers and authorities on request, not on this page. Please allow a reasonable time to fix before disclosing.

Security updates reach the current release through the Mac App Store and the App Store. Anyone on an older release should update to the latest one.

How this is produced

Each component gets a CycloneDX software bill of materials from its pinned lockfile or its Xcode project, and every package in it is checked with Trivy against the OSV.dev database — GitHub advisories, CVE and npm — with npm audit run alongside. Fixed vulnerabilities are counted against the first recorded audit. A machine-readable summary is at status.json.