Privacy policy

Elo Street (elostreet.com) is a free practice site. You can use all of it without an account, and then nothing about you leaves your browser except what any website receives. An account is optional and only keeps your progress and streak across devices.

Last updated: 14 November 2026.

Who is responsible

The site is run by an individual developer. For any question about your data, or to use the rights listed below, write to [email protected].

Without an account

Your progress (solved problems, attempts, hints used, time spent) and your theme choice are saved in your browser's local storage, under keys starting with elostreet:. They are never sent to us. Clearing your browser data deletes them. The stats page can export them to a file and import them back.

No advertising, no tracking cookies, no analytics scripts. The site sets no cookies of its own.

With an account (optional)

Accounts are handled by Supabase (authentication and database). When you create one we store:

Sign-in details. Your email address and, if you sign in with email, a password stored only as a secure hash. If you sign in with Google or GitHub, we receive from them your email address, name and profile picture link. We never see your Google or GitHub password. Your sign-in session is kept in your browser's local storage.
Your username, which you choose (3 to 20 letters, digits or underscores).
Your progress, the same data as in your browser: per problem, whether it is solved or seen, attempts, hints used, time spent and dates.
Your daily results: for each day you played, which problem, and whether you solved it that day.

What other people see: on the public leaderboard, your username, your current streak, your best streak and the number of days you solved. Nothing else, and your email address is never shown to anyone.

Why we use it

Only to run the service you asked for: signing you in, keeping your progress on all your devices, and computing the leaderboard. We do not sell or share your data and do not use it for advertising.

Service providers

Supabase: accounts and database.
Cloudflare: hosting and network.
Google and GitHub: only if you choose to sign in with them. Their own privacy policies apply.
Google Fonts: web font delivery.

How long we keep it

Account data is kept as long as your account exists. You can delete your account at any time from the account page: this deletes your account, username, progress and daily results. Data in your browser stays until you clear it.

Your rights

If you are in the EU/EEA or the UK, you can ask to access, correct, export or delete your data, or object to its use, by writing to the address above. You can also complain to your national data protection authority.

Children

The site is for people aged 13 and over. Accounts should not be created by anyone under 13. If you are under the age at which you can consent to data processing in your country (for example 15 in France), a parent or guardian should agree before you create an account.

Changes

If this policy changes, the new version will be posted on this page with a new date.