Disclaimer

Please read this disclaimer carefully before using prochess.online. By using this site, you acknowledge and accept the limitations described below. Last updated: July 2026.

1. Automated Analysis Disclaimer

All chess analysis, move classifications (Brilliant, Best, Excellent, Good, Inaccuracy, Mistake, Blunder), accuracy scores, opening identifications, evaluation scores, and engine continuations provided by prochess.online are generated entirely by automated software (Stockfish 18 chess engine) running inside your browser.

These outputs are the result of algorithmic computation based on chess engine search trees and neural network evaluation — they are not the product of human chess expertise, titled player judgment, or professional coaching analysis.

2. Engine Accuracy Limitations

While Stockfish 18 is one of the strongest chess engines in existence, it has fundamental limitations that users must understand:

• Search depth matters. At the Blitz preset (0.8 seconds per move), the engine may miss deep tactical sequences that a longer analysis would catch. The Deep preset (3 seconds) is more reliable but still bounded by search time.
• Positional evaluation is imperfect. The engine's neural network evaluates positions based on patterns learned from training data. It can misjudge positional nuances, especially in highly unusual or imbalanced positions.
• Horizon effect. The engine may misevaluate positions where the critical line lies just beyond its search depth — a well-known limitation of all alpha-beta chess engines.
• Endgame tablebase gaps. Stockfish 18 in the browser does not have access to endgame tablebases. Certain theoretical endgame positions may be misjudged without tablebase access.
• Opening book limitations. Opening classification depends on the completeness of our ECO database. Uncommon or very recent opening lines may not be identified correctly.

3. Not Professional Advice

prochess.online is an automated tool — not a substitute for human chess instruction.

The move classifications, engine continuations, and analysis provided by this Service do not constitute professional chess coaching, instruction, or advice. They should be used as one of many tools in your chess improvement toolkit — alongside studying with a qualified coach, analyzing games with stronger players, reading chess literature, and practicing tactics.

Decisions you make based on engine analysis — including adopting specific openings, strategies, or playing styles — are made at your own discretion and risk.

4. No Guarantee of Outcomes

prochess.online makes no guarantee, express or implied, that using this Service will improve your chess rating, tournament performance, or overall chess ability. Chess improvement depends on numerous factors including consistent practice, quality of study, natural aptitude, quality of opponents, and many other variables beyond the scope of any analysis tool.

5. Third-Party Data Disclaimer

When you import games from Chess.com or Lichess via their public APIs, the game data comes from those third-party platforms. prochess.online does not verify the accuracy, completeness, or authenticity of third-party game data. The PGN parsing and engine analysis are performed on whatever data is received.

6. Technical Reliability

While we strive to maintain a reliable service, prochess.online may occasionally be unavailable due to hosting issues, maintenance, or factors beyond our control. The WebAssembly engine may fail to initialize on some browsers or devices, particularly older ones without WebAssembly or SharedArrayBuffer support.

7. Use at Your Own Risk

Any reliance you place on the information, analysis, classifications, scores, or any other output from prochess.online is strictly at your own risk. We shall not be held liable for any loss, damage, or negative outcome resulting from your use of this Service.