Last updated October 11, 2026
Privacy Policy
Who we are
Stamp Lens (“the app”) is provided by the Stamp Lens team (“we”, “us”). We are the controller of the limited data described below. Contact: support@stamplens.app.
The short version
- There is no account. We don’t ask for your name, email or phone number.
- Your full photo stays on your phone. When you scan, only the cropped stamps are sent, with location and other photo metadata removed.
- Your collection (stamps, albums, notes, your own catalog numbers) is stored on your device.
- We don’t sell data, show ads, or track you across other companies’ apps and websites.
Camera and photos
The app uses the camera, or a photo you pick from your library, to find stamps. Finding and cropping each stamp happens on your phone. Nothing is sent until you start a scan.
What happens when you scan
To identify a stamp, the app sends a request to our recognition server (api.stamplens.app) containing:
- The stamp crops: JPEG images, at most 1024 pixels on the long side, with EXIF data (including GPS location) removed.
- An anonymous app user ID: a random ID created by our subscription provider (RevenueCat). It is used to apply free and Pro scan limits. It is not linked to your name or email.
- A device check token: from Apple App Attest (iPhone) or Google Play Integrity (Android), which proves the request comes from the real app and helps us block abuse.
- Your IP address: seen by any server you connect to. We use it only for rate limiting and abuse protection.
The server turns each crop into a numeric “fingerprint” (an image embedding) and compares it with the images in our own stamp catalog. For hard cases, where the closest matches are too similar to call, the crop and short facts about the candidate stamps may be sent to Anthropic’s Claude, an AI model, which picks among our real catalog entries and reads text on the stamp. Claude never sets values.
How long we keep scan data
- Crops: processed to answer your scan and not stored on our server.
- Results: the answer for a crop (not the image) is cached for up to 24 hours under a one-way hash of the image, so a rescan of the same photo gets the same answer.
- Help improve recognition: an optional setting, off by default. If you turn it on, we may keep your crops for up to 24 months to improve recognition. You can turn it off at any time and ask us to delete them.
- Limits: scan counters per anonymous ID and per IP address reset daily or within minutes.
Services that receive data
| Service | What it receives | Why |
|---|---|---|
| Cloudflare (Workers, D1, Vectorize, KV) | Scan requests as described above, IP address; also hosts this website | Runs the recognition server, the stamp catalog and this site |
| Image embedding service | Stamp crop images (no IDs) | Computes the image fingerprint used to search the catalog; runs on a cloud GPU provider we choose |
| Anthropic (Claude API) | For hard cases only: a stamp crop and facts about candidate catalog stamps (no IDs) | Picks the right catalog entry and reads printed text. Under Anthropic’s commercial terms, API data is not used to train its models. |
| Apple App Attest, Google Play Integrity | A device integrity check created by your phone | Blocking scripted abuse of the recognition server |
| RevenueCat, Apple, Google | The anonymous app user ID and purchase status or history if you subscribe | Managing Pro subscriptions. Payments are handled by the App Store or Google Play; we never see your card. |
| PostHog (EU servers) | Anonymous usage events such as “scan completed” with counts, app version, platform, store country and language, the anonymous app user ID, and error codes | Finding bugs and learning which features are used |
Analytics never include photos, crops, anything you type (notes, catalog numbers, album names), names or precise location. We don’t link analytics to your identity.
Data stored on your device
Your scans, crops, saved stamps, albums, wishlist, notes and catalog numbers are stored in the app’s private storage on your phone. We never receive them unless you send them to us. Deleting the app deletes them. Export (CSV or PDF) creates a file you choose where to share.
When you contact us
If you email support, we receive your email address and what you write, plus anything you attach (for example a stamp photo when you report a wrong result, which the app only attaches if you say yes). We use it only to answer you and to fix the problem.
This website
stamplens.app sets no cookies and runs no analytics or ads. Cloudflare, which hosts it, processes your IP address to deliver the pages and protect the site.
Your rights
Depending on where you live (for example under the GDPR or CCPA), you can ask to access, correct or delete data we hold about you, or object to its use. Because we don’t know who you are, include anything that helps us find your data. Write to support@stamplens.app. You can also complain to your local data protection authority.
International transfers
Our providers may process data outside your country, including in the United States. Where the law requires it, transfers are covered by the providers’ data processing terms, such as the EU Standard Contractual Clauses.
Children
Stamp Lens is not directed at children under 13, and we don’t knowingly collect their data.
Changes
If the app starts handling data differently, we’ll update this page and the date at the top before the change ships.