Last updated: 12 May 2026
This privacy policy covers the Textbook of Usability website (textbookofusability.com) and the companion macOS app Caliper. Both are produced by Dr Chris Paton at the University of Auckland.
Short version
- The website doesn't collect anything personal. It serves static HTML, CSS, and JavaScript files. There are no accounts, no trackers, no third-party analytics scripts, no advertising.
- Caliper for Mac doesn't collect anything either. No telemetry, no analytics, no accounts. Audits run on your Mac and stay on your Mac.
What Caliper does on your computer
When you use Caliper to audit a website:
- The app loads the URL you typed into an embedded WebKit view — the same engine Safari uses. This is a direct connection from your Mac to that website, no proxying through any server we run. The website you audit will see your IP address and User-Agent string in the normal way that any web browser would expose them.
- A page snapshot, computed scores, and the issue list are saved
to your Mac's sandboxed Application Support folder
(
~/Library/Containers/com.textbookofusability.caliper/...). Nothing is uploaded. - If you export a PDF, Markdown, or JSON report, the file is written to a location you choose via the system save panel. We don't see or store it.
What we don't do
- We don't collect device identifiers, advertising IDs, or fingerprints.
- We don't use Google Analytics, Plausible, Fathom, or any other analytics service on the website or in the app.
- We don't sell, share, or transmit your audit data anywhere.
- We don't fingerprint or profile users.
- There is no account system, so there's nothing to register, log in to, or delete.
Third parties
- Apple App Store. If you bought Caliper through the Mac App Store, Apple collects purchase and download information per Apple's own privacy policy. We don't see this data beyond the aggregate sales numbers Apple shows in App Store Connect.
- Google Fonts. The textbook website (not the app) loads the Libre Baskerville typeface from fonts.googleapis.com. Google's font-serving terms apply. The app uses system fonts only and doesn't make this request.
- Websites you audit. When Caliper loads a URL for analysis, that website's own privacy policy and terms apply to whatever it serves back. We don't act as an intermediary or modify the traffic.
Children
Neither the textbook nor Caliper is directed at children under 13. We don't knowingly collect any information from anyone, so there's nothing to disclose specifically about minors.
Changes to this policy
If the policy changes materially, we'll update the date at the top of this page. The most recent version is always at textbookofusability.com/privacy.
Contact
Questions: cpaton@gmail.com
Postal: Dr Chris Paton, University of Auckland, New Zealand.