Cookie Policy
Last updated: 3 August 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 the fact that you have already seen our cookie notice.
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: none
20cards sets no analytics cookies at all. We used Google Analytics 4 until 3 August 2026, behind an explicit opt-in; it has been removed entirely, and with it the _ga cookies it used to set. Nothing replaced it that stores anything on your device — see the next section.
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 that you have seen the cookie notice, so it isn't shown 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 — there is nothing to opt out of: the only cookies we set are the strictly necessary ones listed above, and they are required for signing in. Use the Cookie notice link in the footer to re-read this notice at any time.
- 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. Blocking our strictly necessary cookies will prevent you from staying signed in.
Third-party policies
You can read the privacy policies of the services that process data on our behalf here: