Cookie Policy
Last updated: 15 April 2026
This page explains which cookies and similar technologies 20cards uses, what each of them is for, and how you can manage your preferences. For the full picture of how we process personal data, see the Privacy Policy.
What are cookies
Cookies are small text files that a website asks your browser to store on your device. They let the site recognise you between visits, keep you signed in, or collect anonymous statistics. This page also covers similar technologies like browser localStorage, which we use to remember your in-progress deck builds and your cookie choice.
Strictly necessary cookies
These cookies are required for the site to work and cannot be turned off. They do not track you and are not used for analytics or marketing.
| Name | Purpose | Duration |
|---|---|---|
| sb-*-auth-token | Keeps you signed in across page navigations (Supabase authentication) | Session / up to 1 year |
| sb-*-auth-token-code-verifier | Secures the OAuth PKCE login flow against interception | Login flow only |
Analytics cookies (optional)
We load Google Analytics 4 only after you explicitly accept analytics cookies via the consent banner. Until you give consent, no GA script is injected and no _ga cookies are set. You can change your mind at any time using the Cookie preferences button in the footer.
| Name | Purpose | Duration |
|---|---|---|
| _ga | Google Analytics 4 client identifier — distinguishes unique visitors | 2 years |
| _ga_97WLBPWYVG | Google Analytics 4 session state for the 20cards property | 2 years |
Cookie-less analytics
We also use Vercel Analytics and Vercel Speed Insights to measure performance and reliability. These services are cookie-less and aggregate usage without identifying individual visitors. No opt-in is required because they rely on legitimate interest under GDPR Article 6(1)(f).
Browser local storage
20cards uses your browser's localStorage to remember things locally on your device. None of these are cookies and none of them are sent to our servers in background requests.
| Key | Purpose |
|---|---|
| 20cards-deck-builder | Saves your in-progress deck build so it survives a page refresh |
| 20cards-cookie-consent | Remembers your cookie preferences so we don't ask again |
| 20cards-anon-deck-ids | Tracks decks you create without an account so they can be claimed by your profile if you sign up later |
How to manage cookies
- On 20cards — use the Cookie preferences link in the footer to re-open the consent banner and change your choice.
- From your browser — all modern browsers let you view, block, or delete cookies and local storage for individual sites. Check your browser's “Privacy & Security” settings.
- Via Google's opt-out — for Google Analytics specifically, you can install Google's official opt-out browser add-on at tools.google.com/dlpage/gaoptout.
Third-party policies
You can read the privacy policies of the services that process data on our behalf here: