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Privacy at Chess Doctrine

No accounts, no names, no emails, no payments and no ads. The little data we keep, you can withdraw or erase at any time.

The short version

  • We use one cookie of our own (about 400 days) so the site can tell browsers apart.
  • Google Analytics sets its own cookies so we can see how the site is used and where visitors come from (analytics and marketing).
  • We keep a log of your learning events so your progress works.
  • Your IP address is stored only as a keyed hash, never in plain form.
  • You can withdraw consent or erase your data at any time, feature by feature, right on the site.

1. What we collect, why, and for how long

1.1 A browser cookie (cdx_anon, about 400 days)

A signed random token that lets us tell browsers apart. It contains no personal data: it is a random string, signed so it cannot be forged.

Why
Your settings, your diagnosis jobs, your progress.
Legal basis
Legitimate interest (making the service work).
Stored
On your device; we keep only the derived anonymous ID.
How to disable
Delete or block cookies in your browser settings. The site still works, but every visit looks like a new visitor, so there is no progress history.

1.2 A log of learning events

When you analyze games, solve puzzles or use the Elo estimate, we add small events to our log: which feature was used, the time control and aggregated statistics (for example, move counts per game and sums of model scores). We do not currently store the raw PGN of your games. If we ever store game text, it will need a separate opt-in ("pgn-storage"), and opponents' nicknames will be replaced with "Opponent #N".

Why
Tracking your progress and improving the product.
Legal basis
Legitimate interest; "reveal" events (sharing your rating) only with your explicit consent.
Stored
Until you withdraw consent or ask for erasure (see section 3).

1.3 Technical data

Your IP address is used to prevent abuse (rate limits) and is stored only as a keyed hash (HMAC).

1.4 Google Analytics (cookies _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 shows us which guides people read and which channels are worth our time. Google processes this data as described in its partner-sites policy.

Why
Analytics and marketing (understanding readers and where they come from).
Legal basis
Your consent, given through the cookie notice on the site.
Stored
The cookies on your device for up to 2 years; detailed reports in Google Analytics for the retention period set in our account (2 to 14 months).
How to disable
Block or delete cookies in your browser, or install Google's opt-out add-on. The site works the same.

1.5 What we do not collect

We do not collect names, email addresses, passwords, payment data, precise location or device fingerprints.

DataPurposeBasisMax retention
cdx_anon cookieService works, progressLegitimate interestAbout 400 days (your device)
Learning events logProgress, product improvementLegitimate interestUntil consent is withdrawn or the data is anonymized
Rating-reveal eventsShow your rating estimateConsent (opt-in)Until consent is withdrawn
IP (HMAC hash only)Abuse preventionLegitimate interestRate-limit window
Google Analytics cookies and visit dataAnalytics, marketingConsent (cookie notice)Cookies up to 2 years; reports 2 to 14 months

2. Cookies

We use one cookie of our own (cdx_anon, about 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), and strictly necessary technical storage on your device (your settings). You can delete or block cookies in your browser settings at any time. The site stays usable, but your progress will not carry over.

3. Your rights and how erasure works

At any time, feature by feature, you can 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 do not know who you are (GDPR Art. 11), we handle such requests by your browser's identifier. Send the request from the same browser, and we will:

  1. Rotate your identifier. Your old anonymous ID is detached from your browser immediately.
  2. Anonymize the old log within 30 days. An automated job removes the indirect identifiers (ratings, game dates, platform game IDs) from past events, after which they can no longer be linked to you. Backups, if any, are purged on their own cycle within 6 months.

You also have the rights of access, rectification, restriction, portability and objection, and the right to complain to your data protection authority. Please write to us first at media@chessdoctrine.com. We answer within 10 working days (152-FZ) or one month (GDPR).

4. Who sees the data

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.

5. Children

The site is intended for users 14 and older. Users under 14 should use it together with a parent or guardian, who gives (and may withdraw) consent. In the US, the minimum age is 13; in the EU, it is your country's digital consent age (13 to 16). We never ask for a child's name or email. If you are a parent and believe your child uses the site without your consent, write to media@chessdoctrine.com and we will erase the data linked to their browser within 30 days.

6. Changes to this page

If we change something important, we will show a notice on the site. We have no email list, so the site is where you will see it.

Last updated: October 2026 · Contact: media@chessdoctrine.com