Privacy policy

Last updated: 7 November 2026

1. Summary

  • COSTLY sets no cookies and uses no ads and no cross-site tracking.
  • We count visitors with Vercel Web Analytics – without cookies and without storing anything on your device.
  • There are no accounts. Your game progress stays in your browser on your device.
  • For “How everyone guessed” we count answers only anonymously and in aggregate. We store neither your IP address nor any identifier.
  • When you open the site, our hosting provider processes technically necessary access data.

2. Controller

Casian Nowak
Email: Casian_nowak.socials@icloud.com

3. Hosting and server logs

The website is hosted by Vercel Inc. (USA). On every request Vercel processes technically necessary data: IP address, date and time, requested URL, referrer, browser and operating system. This is needed to deliver the site, keep it secure and fix errors. The legal basis is our legitimate interest in a secure, working service (Art. 6(1)(f) GDPR).

We have a data processing agreement with Vercel (Art. 28 GDPR). Transfers to the USA are based on the EU-US Data Privacy Framework or EU standard contractual clauses. Vercel keeps log data only for a short time. More: Vercel privacy policy.

4. Visitor statistics (Vercel Web Analytics)

To understand how many people use COSTLY and how they find it, we use Vercel Web Analytics by Vercel Inc. (USA). On each page view it records the page, the referring page, country, browser, operating system and device type. No cookies are set and nothing is stored on your device. Visitors are not recognised across days or websites; according to Vercel, a short-lived value derived from the request is used for this and is not stored permanently. We only see aggregated statistics, never individual people.

The legal basis is our legitimate interest in improving the service and measuring its reach (Art. 6(1)(f) GDPR). Transfers to the USA are covered as for hosting (section 3). More: Vercel Web Analytics.

5. Storage in your browser (local storage)

So you can continue a game and keep your stats, records, streak and settings (e.g. light/dark mode), COSTLY saves them in your browser’s local storage. They stay on your device and are not sent to us. This storage is strictly necessary for the feature you use (§ 25(2) no. 2 TDDDG). You can delete it at any time with “Reset progress” in the settings or in your browser.

6. Anonymous game statistics

When you answer a question, your browser sends the question ID and your guess to our server. There we only count which rounded range the guess falls into; the guess itself is not stored. When you finish the Daily Challenge, the day’s player count and point total go up by one and by your score. Only these totals are stored – no IP address, identifier or anything else linked to you. The daily counters are deleted automatically after 14 days.

For storage we use the Upstash database (Upstash, Inc.) as a processor; the storage location depends on the chosen database region. The legal basis is our legitimate interest in letting players compare themselves with others (Art. 6(1)(f) GDPR).

7. Photos, fonts and links

Photos (from Wikimedia Commons) and fonts are served from our own server, so opening the site makes no connection to Wikimedia, Google or other third parties. Links to sources, Wikipedia or Wikimedia Commons only open other sites when you click them; their privacy policies apply there.

“Share result” copies your result to the clipboard or opens your device’s share menu. No data is sent to us.

8. 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 GDPR). Contact us at the email address above. Because the game statistics contain no personal data, we cannot link any of it to a person.

You can also complain to a data protection supervisory authority, in particular in the country or German state where you live.

9. Changes

We update this policy when the website or the law changes, for example if ads are added in the future. The version published here applies.