Legal

Privacy Policy

Last updated: July 3, 2026

This Privacy Policy explains what data the Chess Mate browser extension (“Chess Mate”, “we”, “us”) collects, why, and how it is handled. Chess Mate is a browser extension that detects chess positions displayed on your screen and adds an overlay offering analysis and study features. We designed it to keep as much as possible on your device.

The short version

• Board detection runs entirely on your device. Screenshots of your screen are analyzed locally by an on-device vision model and are never uploaded to us or to any third party.
• We keep collection minimal. If you create an account, we process your email address and authentication credentials. On Chessable, we also collect book, chapter and variation metadata to build a search index.
• We do not sell your data and we do not use it for advertising or to build user profiles.

Data we collect

Account and authentication data

When you sign up or sign in, we process your email address and password to create and secure your account. Authentication is handled by our processor Supabase; your password is stored only as a salted hash and is never accessible to us in plain text.

Subscription and payment data

If you subscribe to a paid plan, payments are processed by Stripe. Card details are entered on Stripe’s hosted checkout and are handled directly by Stripe — we never receive or store your full payment card information. We retain only the subscription status needed to unlock paid features (e.g. whether your subscription is active).

Data stored locally on your device

To work quickly and offline, Chess Mate stores data locally in your browser (via storage and IndexedDB): the vision model, your preferences and settings, your login session, cached chess positions and games detected during use, and your remaining analysis credits. It also keeps a cache of opening statistics used to render the opening tree; this cache is the largest local dataset and is capped at 50 MB, with the oldest entries evicted automatically once that limit is reached. This data stays on your device and is not transmitted to us, except for the account data described above.

Chessable library metadata

When you use Chess Mate on Chessable, the extension reads metadata about books, chapters and variations (such as titles, structure and move lists) and sends it to our server. We use this metadata to build and maintain a search index that lets you find courses and variations by position and navigate between them. This is the only website content the extension transmits off your device — screen captures are never uploaded.

Screen captures

To detect a chessboard, the extension periodically captures an image of the active tab while it is running, so it can recognize a board as soon as one appears on screen. Each image is processed locally, in your browser, to recognize the position and is discarded immediately afterward. Captures are never uploaded, stored remotely, or shared.

How we use data

• To create, authenticate and secure your account.
• To provide the extension’s features and remember your settings.
• To manage paid subscriptions and unlock corresponding features.
• To build and maintain the Chessable search index that powers course and position navigation.
• To respond to your support requests.

We do not use your data for advertising, we do not build advertising or user profiles from it, and we do not use it to determine creditworthiness or for lending purposes.

Sharing and third parties

We do not sell or transfer your personal data to third parties, except to the service providers strictly required to operate Chess Mate, acting on our behalf:

• Supabase — authentication and database hosting for account data.
• Stripe — payment processing for subscriptions.

We may also disclose data if required by law or to protect our rights and the safety of our users.

Browser permissions

Chess Mate requests the minimum permissions needed for its single purpose:

• storage / unlimitedStorage — to store the vision model, your settings, session and cached data locally. unlimitedStorage is needed mainly for the opening-tree cache, which can grow large (capped at 50 MB) and would otherwise risk being evicted under the default quota.
• activeTab and host access — the extension needs to read and capture the page you are viewing on any site. It takes periodic screenshots of the active tab so a chessboard can be detected locally as you browse (these captures stay on your device), and on Chessable it reads book, chapter and variation metadata from the page to build the search index described above. Host access across sites is required because a board can appear on any page, and because captureVisibleTab only works with it.

Data retention

We keep your account data for as long as your account exists. Locally stored data remains until you clear it or remove the extension. You can delete your account at any time by contacting us, after which we delete the associated personal data, subject to any legal retention obligations.

Your rights

Depending on where you live (including under the EU/EEA GDPR), you have the right to access, correct, delete or export your personal data, to restrict or object to its processing, and to withdraw consent. To exercise these rights, contact us at the address below. You may also lodge a complaint with your local data protection authority.

Changes to this policy

We may update this Privacy Policy from time to time. When we do, we will revise the “Last updated” date above. Material changes will be communicated through the extension or our website.

Contact

For any question or request regarding this policy or your data, contact us at contact@chess-mate.io.