Terms of Service

Last updated: 2026

1. Using the site

Lightness Review is a free chess analysis tool. You may use it for personal, non-commercial purposes. You don't need an account, and we don't ask for any personal information.

2. Copyright — no copying the code

You are prohibited from copying, redistributing, or reusing any part of this website's code — HTML, CSS, JavaScript, or assets — in your own project, whether public or private, without prior written permission. This includes republishing it, hosting it elsewhere, or incorporating it into a derivative work. Viewing the source in your browser for the purpose of understanding how the site works is fine; using any substantial portion of it as the basis for another project is not.

3. Chess engine and third-party software

Game analysis and Coach games run on Stockfish, which is © the Stockfish developers and licensed under the GNU GPL v3. The GPL grants you rights to the Stockfish code itself — those rights are unaffected by these terms. Sections 2 and 5 of these Terms do not apply to the Stockfish engine or to any other third-party software listed on the Credits page.

Importing games uses the public Chess.com and Lichess APIs. Your use of those services is subject to their own terms.

4. No warranty

Lightness Review is provided "as is" and without warranty of any kind. Engine evaluations and move classifications are heuristic and can be wrong. We make no guarantee about the accuracy, availability, or fitness of the site for any particular purpose. Your use of the site is at your own risk.

5. Your data

Your review history and statistics are stored in your browser only and are never uploaded. See the About page for the full privacy picture. Because we can't see your data, we can't recover it if you clear your browser storage — use the export feature on the Stats page to keep a backup.

6. Changes

These terms may be updated from time to time. If the changes are significant, the acceptance prompt will reappear the next time you visit the site. Continued use after that point means you accept the new terms.

7. Contact

Questions about these terms? Use the feedback link in the footer of any page.