trolls.dev
06 The inspector — case study

Preflight

Check your PDF before it flies.

A native macOS utility that checks a PDF against real submission limits — exact bytes, page count, searchable text, encryption — and, when it's too big, builds a verified copy that fits. The original is never touched, and nothing ever leaves your Mac.

Status
Coming soon
Platform
macOS 14+
Privacy
Local-only
Field
PDF · Utilities
Ask us about Preflight → All work
Preflight — quarterly-report.pdf
Preflight report Profile · Email
✓ File size 4,618,204  / 5,000,000 B
Optimizing…
  • ✓ Pages 12 · within 20 max
  • ✓ Searchable text every page
  • ✓ Encryption none — opens clean
source · untouched Cleared for submission
The worst place to learn the file limit is the upload form. The bet behind it

Why we built it

“File exceeds the maximum size” — at 4:58 PM, on the day it's due.

Every submission portal, court filing system, journal, and email server has rules: a size ceiling, a page cap, text that must be searchable, no encryption. And almost all of them share the same design flaw — you discover the rules by breaking them, at the upload form, after the work is finished and the deadline is close.

The fixes people reach for are worse: a sketchy “compress PDF online” site you feed a confidential document to, or a re-export roulette that silently flattens the text your recipient needs to search. The document was never the problem. Knowing whether it would be accepted was.

Preflight runs the checklist at your desk, so the upload form has nothing left to say.

What we made Four moves
  1. 01

    Checked to the byte

    Pick a limit — the classic email-attachment ceiling or your own exact number — and Preflight measures the PDF against it in bytes, not vibes. Page count, searchable text, encryption, and page dimensions get the same treatment: observed value, requirement, verdict.

  2. 02

    Optimize to fit, never overwrite

    When a PDF is over the limit, Preflight builds a separate, locally optimized copy at or below the exact target — preserving page geometry and searchable text — and verifies it independently before it lands. The source file is never touched.

  3. 03

    Proof you can keep

    Reverify both files against their SHA-256 hashes, compare them side by side with synchronized pages and zoom, and export a receipt with exact original, output, target, and savings byte counts. Batch runs of up to 100 PDFs get a JSON or CSV receipt of their own.

  4. 04

    Nothing leaves the Mac

    No network requests, no accounts, no analytics. Even the on-device Apple Intelligence explanations are composed only of verbatim passages verified against the PDF's own text, held in memory and never written to disk.

Choices we sweated

A utility you hand your most important file.

The source is sacred

Preflight never modifies, moves, or overwrites the PDF you selected. Optimization always creates a new file, staged in a private directory and published with an atomic rename — and if no safely preserved candidate can meet the target, it refuses rather than degrade your document.

Exact numbers, honestly reported

A limit is a number, so the report is numbers: observed bytes against required bytes, hashes recalculated before every comparison, receipts that record exactly what was measured. No 'about 5 MB' — the upload form won't round in your favor, so Preflight doesn't either.

No network, on principle

The app has no network code at all. That isn't a privacy-policy promise held together by good intentions — it's an architectural fact, which makes the policy the easiest one we've ever written.

Further reading from the journal

The thinking behind a tool this small and this single-minded is in our note In defense of small software — and why we only build things we run ourselves is in Why we only build what we run.

Preflight has its own privacy policy, a support page, and a user guide. It runs entirely on your Mac and performs no network requests.

Colophon End of Case Study 06

Cleared for submission, before you hit send.

Preflight is headed for the Mac App Store. Drop us a line if you want to know the moment it lands — or tell us which submission portal's rules still bite you.

Get in touch → Next case study: ganttchart.ai →