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Anti-Cheating & Fair Play: How Chess Servers Catch Cheaters

The greatest threat to the integrity of online chess is engine assistance. It is incredibly easy for a player to open a chess engine in another browser tab. However, it is actually incredibly hard to get away with it for long. Modern chess servers use sophisticated statistical algorithms to detect and ban cheaters.

1. How Detection Works: The "Fingerprint"

You might think cheating is detected simply by checking "did they play the computer move?" It is much more complex. Fair Play teams analyze thousands of data points to create a "fingerprint" of a player's style.

Centipawn Loss (ACPL)

ACPL (Average Centipawn Loss) measures how much "value" a player loses per move compared to the perfect engine move.

Grandmasters: Typically have an ACPL of 15-25. They play great moves, but they are human.
Engines: Have an ACPL of near 0.
The Red Flag: If a 1500-rated player consistently plays games with an ACPL of 5, it is statistically impossible. The system flags them immediately.

The "Ken Regan" Method (Z-Scores)

Professor Ken Regan developed the statistical standard used by FIDE. His model calculates a "Z-Score"—the probability that a human of a specific rating could find a specific series of moves. When the probability drops to 1 in millions (a high Z-score), cheating is the only scientific explanation.

Time Usage Patterns

Humans think differently in complex positions than in simple ones. We might spend 10 minutes on a tactical complication and 10 seconds on a recapture. Cheaters (who are relaying moves from another window) often use a uniform amount of time (e.g., exactly 10 seconds per move) regardless of complexity. Algorithms look for this unnatural rhythm.

2. The Vital Distinction: Engines vs. Databases

For Correspondence (Turn-Based) players, the rules are different from Blitz, and this often causes confusion.

✅ Allowed: Databases & Books: In most correspondence tournaments (including on ChessWorld), you are allowed to look up opening moves in a database (like a "Game Explorer") or a physical book. This is considered "Research," similar to a student studying for an exam.
❌ BANNED: Engines: You are never allowed to let a computer engine (Stockfish, Komodo) decide the move for you. You cannot use software that says "White is winning, play Nf3."

Always check the specific rules of your tournament, but this is the general standard for correspondence play.

3. Other Forms of Cheating

Sandbagging: Deliberately losing games to lower your rating. This is often done to enter tournaments restricted to lower-rated players to win easy prizes. It is a serious violation of fair play.
Multi-Accounting: Creating a second account to test openings or manipulate ratings is generally forbidden.

4. Coping with Paranoia

If you lose a game, do not automatically assume your opponent cheated. Even lower-rated players play brilliant tactical sequences sometimes. Focus on your own mistakes. Trust that the server's detection methods are working in the background to keep the playing field level.