No accounts, no names, no emails, no payments, no ads — and what little we do keep, you can withdraw or erase anytime.
cdx_anon, ~400 days)A signed random token that lets us tell browsers apart. It carries no personal data — it's a random string we sign so it can't be forged.
When you analyze games, solve puzzles, or use the Elo estimate, we append small events to our log: what feature was used, time control, and aggregated statistics (for example, per-game move counts and model score sums). Raw PGN of your games is NOT stored today — if we ever store game text, it will be under a separate opt-in ("pgn-storage"), and opponents' nicknames are replaced with "Opponent #N".
Your IP address is used to prevent abuse (rate limits) and is stored only as a keyed hash (HMAC).
_ga and _ga_4M9BVJB66K, up to 2 years)We use Google Analytics 4, loaded through Google Tag Manager, to collect data for analytics and marketing: which pages are visited, how long people stay, which sites and searches bring them here, and the device, browser and approximate location (country or city, derived from the IP address by Google). It tells us which guides people read and which channels are worth our time. Google processes this data as described in its partner-sites policy.
Names, email addresses, passwords, payment data, precise location, device fingerprints — none of it exists here.
| Data | Purpose | Basis | Max retention |
|---|---|---|---|
cdx_anon cookie | service works, progress | legitimate interest | ~400 days (your device) |
| Learning events journal | progress, product improvement | legitimate interest | until consent withdrawn / anonymized |
| Rating-reveal events | show your rating estimate | consent (opt-in) | until consent withdrawn |
| IP (HMAC hash only) | abuse prevention | legitimate interest | rate-limit window |
| Google Analytics cookies and visit data | analytics, marketing | consent (cookie notice) | cookies up to 2 years; reports 2–14 months |
We use one cookie of our own (cdx_anon, ~400 days), the Google Analytics cookies
(_ga and _ga_4M9BVJB66K, up to 2 years, see 1.4), a small cookie that
remembers you closed the cookie notice (cd_cookie_ok, 1 year), plus strictly
necessary technical storage on your device (your settings). You can delete or block cookies via
your browser settings at any time; the site remains usable, minus continuity of progress.
You can, at any time, per feature: grant or withdraw consent (base log, game storage, rating reveal), and ask us to erase what is linked to your browser (the "delete my data" button on the diagnosis page).
Because we don't know who you are (GDPR Art. 11), we process such requests against your browser's identifier — present the request from the same browser, and we will:
You also have the rights of access, rectification, restriction, portability, and objection; and the right to complain to your data protection authority. But please write to us first — ads.chessdoctrine@gmail.com — we answer within 10 working days (152-FZ) / one month (GDPR).
Service providers may process data only as needed to operate Chess Doctrine. Google receives the visit data described in 1.4 (Google Analytics). We do not sell data or share it with data brokers.
The site is intended for users 14 and older. Under 14 — please use it together with a parent or guardian, who gives (and may withdraw) consent. For users in the US, the minimum age is 13; in the EU, your country's digital-consent age (13–16). We never ask for a child's name or email. If you're a parent and believe your child uses the site without your consent, write to ads.chessdoctrine@gmail.com — we'll erase the data linked to their browser within 30 days.
If we change something important, we'll show a banner on the site (we have no email channel — there's no way to miss it on the site itself).
Last updated: October 2026 · Contact: ads.chessdoctrine@gmail.com
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