Privacy
What Zetlyn keeps, why, and for how long.
Controller
Artur Susdorf
Franz-Sigrist-Str. 6, 79206 Breisach am Rhein, Germany
privacy@zetlyn.com
What Zetlyn does
You name a public web page and, if you like, a place on it. Zetlyn reads that page once an hour from its own servers and emails you when what you marked changes. Your email address is your account; there is no password.
Your account and your watches
What is kept for an account: the email address, when it was made, whether it was confirmed,
whether its free trial was used, whether it has a subscription, and the payment provider's
reference for the customer and the subscription. For each watch: the address of the page, a
description of the place you marked (its position on the page, its tag, its id and
classes, and the text beside it), what was read there, the time and outcome of every check, and
every change with the value before and after.
The legal basis is Art. 6 (1) (b) GDPR: it is what providing the service you asked for requires.
When you end a watch, it is deleted with its checks and changes. A watch you never confirmed is deleted after two days. An account without a subscription is deleted 30 days after its last watch ended, with everything in it. To have your account deleted at once, write to privacy@zetlyn.com.
Confirming by email
The first time an address is used, Zetlyn sends it a link and watches nothing until the link is clicked, so that nobody can have mail sent to an address that is not theirs. The links Zetlyn mails, and the sign-in they open, are 256-bit random values; only a SHA-256 hash of each is stored.
Cookies
One, and only what signing in needs (§ 25 (2) no. 2 TDDDG), so no consent is asked for:
z, your sign-in, for 90 days or until you sign out. It holds a random value and
nothing else, is sent only over https, cannot be read by scripts and is not sent when another
site links or posts here. There are no cookies for analytics or advertising, and no third-party
scripts or fonts on zetlyn.com.
Showing you the page to mark
To let you click the place to watch, Zetlyn reads the page on its servers and shows it to you without its scripts. The page's own images, styles and fonts are then loaded by your browser from the site the page is on, as when you visit that site yourself; that site sees your IP address and browser for those requests. Nothing else of yours is sent to it, and once you have marked the place, every later reading is done by Zetlyn's servers alone.
Hosting
Zetlyn runs on servers rented from Hetzner Online GmbH, Industriestr. 25, 91710 Gunzenhausen, Germany, in its German data centres. Hetzner acts as a processor under Art. 28 GDPR.
Confirmation, sign-in and change mails are sent through the mail server of netcup GmbH, Daimlerstraße 25, 76185 Karlsruhe, Germany, which acts as a processor under Art. 28 GDPR. It sees the address a mail goes to and what it says.
Paying
A subscription is paid at Stripe Payments Europe, Ltd., 1 Grand Canal Street Lower, Grand Canal Dock, Dublin, D02 H210, Ireland, which takes the card or the account, the billing address and the VAT number, and sends the invoices. We never see the card. We tell Stripe how many watches beyond those in the plan an account runs, as a number, so that they can be invoiced. From Stripe we keep whether a subscription is active and Stripe's reference for the customer and the subscription. The legal basis is Art. 6 (1) (b) GDPR, and for what tax and commercial law require us to keep, Art. 6 (1) (c) GDPR; invoices are kept for the ten years those laws require. Stripe's own notice is at stripe.com/privacy.
Server logs
The web server in front of Zetlyn keeps no access log. The program logs errors, each check (the watch, its outcome and the page's address) and the address each mail is sent to, in the server's system log, which removes the oldest entries as it fills.
Contact by email
If you write to us, we process what you send in order to handle the enquiry. The legal basis is Art. 6 (1) (b) or (f) GDPR. We delete it once the matter is settled and no retention obligation stands against it.
Your rights
You have the right of access, rectification, erasure, restriction of processing, objection and data portability, and the right to lodge a complaint with a supervisory authority. You can reach us at privacy@zetlyn.com.
As of 18 October 2026.