Privacy Policy

Last updated: 15 November 2026 · This is a translation; the German version is legally binding.

In short: Your location stays on your device. We only process what your account and your contributions need – and you can delete your account in the app at any time.

1. Controller

We have not appointed a data protection officer because the law does not require one. If you have questions about privacy, just write to the address above.

2. The Sumi app

2.1 Using Sumi without an account

You can use the map, stamp information and guide without signing in. The app loads stamp data from our server. For technical reasons, your IP address, the time of the request and details about the app version or device are transmitted and kept in server logs for a short time. This keeps the service secure and stable (Art. 6(1)(f) GDPR).

Settings such as language, map filters, the cover of your stamp book or places and lines you pin there are stored only on your device.

2.2 Your account

To collect and contribute, you need an account. You can register with an email address and password, or use “Sign in with Apple” or “Sign in with Google”. We process:

• your email address (with “Sign in with Apple” possibly an anonymous relay address from Apple) and your password, which is stored only in encrypted form (as a hash),
• with Apple or Google, the account identifier they provide,
• your display name (initially “Stamper-…”, changeable at any time) and your app language, so our emails reach you in your language,
• timestamps of registration, email confirmation, sign-ins and your acceptance of the terms, and where applicable a role (e.g. moderation) or a suspension.

The legal basis is the performance of our contract with you (Art. 6(1)(b) GDPR). We do not import contacts, friend lists or any other data from Apple, Google, Facebook or other platforms.

2.3 Emails

We only send emails your account needs: the activation email after registration, password reset links and a security notice when your password has been changed. We use Resend (Resend, Inc., USA), sending from a data centre in the EU (Ireland). We process your email address, the content of the email and delivery logs (Art. 6(1)(b) GDPR; for the security notice also Art. 6(1)(f) – protecting your account). We don’t send newsletters. Should we ever offer one, only with your separate consent.

2.4 Your collection and private content

Which stamps you have collected (with dates), your favorites, notes and photos of your own stamp imprints (“stamp book”) are visible only to you. Photos of your imprints are kept in private storage that not even our moderators can access (Art. 6(1)(b) GDPR).

2.5 Public contributions

When you report a new stamp, confirm a stamp (“still there” / “gone”) or upload a photo of a stamp’s location, this contribution is visible to all users together with your display name. For new stamps we store the name, station, operator, the position you set on the map, and an optional description and opening hours.

Photos are resized and stripped of metadata (including GPS location) on your device before upload. We review every photo before it is published, usually within 24 hours. Until then, only you and our moderators can see it.

Legal bases: Art. 6(1)(b) GDPR (providing the features), and for the review Art. 6(1)(f) GDPR (protecting users and third parties from illegal content) and Art. 6(1)(c) GDPR (legal obligations, in particular under the Digital Services Act).

2.6 Reports, blocking and moderation

When you report content, we store the report (reason, optional text) with your account so our moderators can handle it. When you block someone, we store this list to hide that person’s content from you. If the terms are violated, we may remove content and suspend accounts. Legal bases: Art. 6(1)(b), (c) and (f) GDPR. Decisions are made by people, not algorithms.

2.7 Location and notifications

Sumi uses your location only with your permission – to show the map and distances and, if you turn on “Stamps nearby”, to notify you when you get close to a stamp you haven’t collected yet. For this, Sumi uses your operating system’s region monitoring, in the background if you allow it. Your location is never sent to us and is not stored. The only exception: when you report a new stamp, we store and publish the position you set for the stamp on the map.

Notifications are created locally on your device. We do not use push services.

2.8 Camera and photo library

Sumi accesses your camera or photos only when you take or choose a photo yourself.

2.9 Maps, directions, translation and read-aloud

• Map: On iPhone, Sumi shows the map with Apple Maps. Your device loads map tiles from Apple; Apple receives technical data such as your IP address and the area shown. Apple’s privacy policy applies.
• Directions: The “Route” button opens Apple Maps or Google Maps with the destination. From then on, that provider’s terms apply.
• Translate: For descriptions written by other users you can tap “Translate”. This opens Google Translate in the browser, and Google receives the text, your IP address and browser data. This only happens when you tap.
• Read aloud: The Japanese phrases in the guide are spoken by your device’s speech engine – locally, without transmission.
• Links: Links to railway company sources or stamp rallies open third-party websites.

2.10 Servers and data location

Our database, file storage and sign-in are operated for us by Supabase (Supabase, Inc., USA) as a processor (Art. 28 GDPR). The data is stored in a data centre in Tokyo, Japan. The European Commission has issued an adequacy decision for Japan (Art. 45 GDPR). Where Supabase, Inc. has access from the USA, EU Standard Contractual Clauses apply (Art. 46(2)(c) GDPR).

2.11 Retention and deletion

We keep your account data until you delete your account, which you can do at any time in the app under Settings → Delete account. This deletes your account, collection, favorites, notes, photos of your imprints, all photos you uploaded and your stamp reports that haven’t been confirmed yet. Stamps already confirmed by the community remain part of the shared database, but without any link to you.

Server and delivery logs are deleted automatically by the providers after a short time (usually after a few days, at most after about 30 days). We keep reports and moderation decisions as long as needed to handle and document them.

2.12 Age

You may create an account from the age of 16. Younger users need their parents’ permission.

3. This website

The website sumistamps.app is served by Cloudflare (Cloudflare, Inc., USA). When you visit, Cloudflare processes technically necessary data such as your IP address, time, page requested and browser details in order to deliver the page and protect it from attacks (Art. 6(1)(f) GDPR). Cloudflare is certified under the EU-US Data Privacy Framework (Art. 45 GDPR). The website currently sets no cookies and loads no content or fonts from other servers.

4. Contacting us by email

Emails to hello@sumistamps.app are forwarded to the controller’s mailbox via Cloudflare’s “Email Routing”. We process your message and contact details to handle your request (Art. 6(1)(b) or (f) GDPR) and delete them when they are no longer needed and no retention obligations apply.

5. Recipients at a glance

• Supabase, Inc. (USA) – servers and database, data centre in Japan – processor, Standard Contractual Clauses
• Resend, Inc. (USA) – sending account emails from the EU – processor, Standard Contractual Clauses
• Cloudflare, Inc. (USA) – website, DNS and email forwarding – processor, EU-US Data Privacy Framework
• Apple and Google – only if you use their sign-in, maps, directions or translation; they act as independent controllers.

There are currently no other recipients. If new services are added – for example to fund Sumi through advertising – we will update this policy beforehand and ask for your consent where required.

6. Your rights

You have the right of access (Art. 15 GDPR), rectification (Art. 16), erasure (Art. 17), restriction of processing (Art. 18), data portability (Art. 20) and to object to processing based on legitimate interests (Art. 21). You can withdraw any consent at any time with effect for the future (Art. 7(3)). Much of this you can do directly in the app; otherwise an email to hello@sumistamps.app is enough.

You may also lodge a complaint with a data protection supervisory authority (Art. 77 GDPR), for example in the country where you live.

7. No automated decisions

We do not make decisions based solely on automated processing that produce legal effects concerning you (Art. 22 GDPR).

8. Changes

We update this policy when Sumi changes – for example if advertising or paid extras are added later. You will always find the current version here.