Privacy Policy — Diagonal Reader

Effective date: 24 September 2026

Diagonal Reader ("the app") helps you read faster by photographing book pages and returning style-preserving summaries. This policy explains what data the app and its backend process. There are no accounts and no sign-in: the app works anonymously with a random browser identifier stored in your device's localStorage.

Data we process

• Page photos. When you tap the shutter, the photo is sent to our backend and forwarded to our AI provider (OpenRouter, running a Google model) solely to generate your summary. Page images are not stored on our servers; they are kept only in the on-device history in your browser (IndexedDB) until you delete them.
• Anonymous browser identifier. The app generates a random identifier (a uuid: value in localStorage) to count your monthly page allowance and recognise an active subscription. It contains no contact details; a purchase email is stored separately and only for subscribers. Clearing site data resets it.
• Purchase information. Subscriptions are sold and billed by Stripe. We receive only the fact that a subscription is active (plus price and expiry timestamps) — never your payment details. Subscribers' purchase email and invoice numbers are stored alongside the Stripe customer link; restoring moves access so exactly one device ID is active per subscription.
• Page counters. Monthly and daily counters linked to your anonymous identifier are stored in our Cloudflare D1 database to enforce the 100-pages/month free allowance and the subscriber guardrails (500/day, 10000/month).

What we do not collect

No contacts, precise location, advertising identifiers, or analytics SDKs. Your purchase email is kept only if you subscribe, solely to recover your subscription. The camera is used only when you tap the shutter; no photos are taken in the background.

Subscription recovery

Subscribers' purchase email and invoice numbers are stored alongside the Stripe customer link and used only to restore Unlimited on a new device: enter your purchase email and an invoice number from a Stripe subscription invoice. Restoring moves access: exactly one device ID is active per subscription.

Third parties

• OpenRouter (AI summarisation) — receives page photos transiently.
• Stripe (payments) — processes subscriptions under Stripe's own privacy policy.
• Cloudflare (hosting) — serves the app and runs the backend that relays summaries and counts pages.

Retention

Page photos and summaries live only on your device and disappear when you delete them or clear site data. Server-side page counters reset every calendar month. Subscription records are kept while a subscription is active (plus its paid period) and removed on expiry.

Children

The app is a general-audience reading tool and is not directed at children under 13. No children's data is knowingly collected.

Your rights

Depending on where you live (e.g. GDPR, CCPA) you may request access, correction, or deletion of data linked to your browser identifier. See data deletion for the one-minute process: your on-device history deletes instantly in the app, while server-side page counters reset every calendar month and subscription records disappear when the subscription expires. There is currently no support email address; a dedicated address for this domain will be listed here once available.

Changes

Material changes to this policy will be published here with a new effective date. Continued use of the app after a change means you accept it.

Contact

There is currently no public support email. A dedicated address for this domain will be listed here once available.