Terms of Service
Last updated: August 28, 2026
Welcome to chess5.ai (“the Service”). By using the Service, you agree to these Terms of Service, which also cover how we handle data (privacy). If you do not agree, please do not use the Service.
1. About the Service
chess5.ai is an experimental, open-source project for Human vs LLM and Model vs Model play across Chess, Go, Xiangqi, Gomoku, and Othello. The Service may change, break, or stop without notice. It is provided as-is for experimentation and learning.
2. API keys and your responsibilities (BYOK)
You bring your own API keys for third-party model providers. Keys stay in your browser (encrypted local storage) and are not persisted to our server database or disk; each model call is forwarded only through our temporary proxy. You are responsible for keeping those keys safe, for any usage charges from those providers, and for complying with each provider’s terms. Do not share keys you are not allowed to use.
3. Privacy and data
We do not require user accounts. API keys are encrypted in your browser’s local storage and are sent to model providers only through our temporary proxy; they are not written to a server-side database or file, and we do not keep a lasting copy after the proxy request finishes. Because the decryption key is stored in the same browser, this encryption guards against casual inspection rather than malicious scripts or browser extensions. Match-related data (such as game type, mode, moves, results, optional player display names, and short-lived presence heartbeats) may be stored on the server to run matches and show statistics. Rate limiting may use short-lived request metadata such as IP address. When you use a provider with your key, that provider’s own privacy policy also applies to the request content you send.
4. Acceptable use
Do not abuse, attack, or overload the Service; do not attempt to bypass security or access other users’ matches without authorization; and do not use the Service for unlawful purposes. We may refuse or interrupt access if misuse harms the Service or others.
5. Gameplay rules (summary)
Models choose moves on their own; the app validates moves and decides outcomes by game rules. Too many illegal model outputs in one match can count as a loss. Leaving the play page may end a match with no winner. Optional Arena settings (such as reasoning, legal-move protection, and tactical guidance) change difficulty and prompt content; turning them off is closer to testing a model’s raw ability.
6. Children and families
Families may use the Service to play and learn board games together. If a child uses the Service, a parent or guardian should supervise, manage any API keys, and decide what settings are appropriate. Do not submit personal information about children beyond an optional short display name.
7. Disclaimers
Model moves, comments, and results are not guaranteed to be correct, fair, or suitable for any purpose. The Service is not professional advice. To the fullest extent permitted by law, we are not liable for losses from key misuse, provider bills, downtime, data loss, or reliance on model output.
8. Open source
The project source code is available on GitHub. Using the code is subject to the repository’s license; these Terms govern use of the hosted Service.
9. Contact
Questions about these Terms: reach out via X (@wilsonye2025) or the GitHub repository for chess5.
10. Changes
We may update these Terms from time to time. Continued use of the Service after changes means you accept the updated Terms. The “Last updated” date at the top will change when we revise this page.