Terms of use

The deal

Everything on Chess411 is free to use. There is no account to create, nothing to buy, and no subscription. In return, the service is offered as it is, and we ask that you use it fairly. How we handle data is its own document, the privacy policy, and it is part of the deal too.

Fair use

• Use Chess411 personally and at a human pace. Don't flood the servers with automated requests, scrape the service, probe it for weaknesses, or try to get around the rate limits and bot checks; they are what keep the tools free for everyone.
• Don't use Chess411 to break another service's rules. If a site you play on forbids engine assistance during games, analysing with Chess411 mid-game is between you and them, and their rules apply.
• Don't use the service for anything unlawful.

We may slow down or block use that ignores this section, and that is the whole of our enforcement: there are no accounts to suspend.

What's yours

The games, positions and images you bring to Chess411 stay yours. By analysing or uploading them you give us just enough permission to do the thing you asked: run the engine over them, read the position out of a screenshot, and show you the result. When you send feedback, you let us keep it and use it to fix and improve Chess411.

What's ours, and what's free software

The Chess411 name, the site and app themselves, and the words and design in them belong to MPL Ventures, LLC. The analysis is powered by Stockfish, free software we ship under the GPL v3, and the puzzles are built on openly licensed data; the exact versions, sources and licenses are on the licenses and credits page. Nothing in these terms takes away any right the GPL gives you.

About the engine's advice

Stockfish is strong, but its verdicts, accuracy scores and coaching lines are automated analysis, not truth. Depths are limited, scanners misread the occasional pawn, and a line that is best for an engine is not always best advice for a human game. Use the output as training and entertainment; decisions you make with it are your own.

No warranty, and our liability

Chess411 is provided as is and as available, without warranties of any kind, express or implied. It may be wrong, slow, down, changed, or one day discontinued, without notice. To the maximum extent the law allows, MPL Ventures, LLC is not liable for any indirect, incidental or consequential damages arising from your use of Chess411, and since the service is free, our total liability for anything connected to it is limited to the amount you paid us: nothing. Where the law grants you rights that cannot be limited this way, those rights are unaffected.

Governing law

These terms are governed by the laws of the State of Illinois, USA, without regard to its conflict of law rules, and any dispute belongs to the courts located in Illinois. If a court finds part of these terms unenforceable, the rest stands.

Changes and contact

If the terms change, this page changes and the date at the top moves; continuing to use Chess411 after that means you accept the new terms. Questions go through Send feedback in the footer.