Castling Rights Checker
Check standard (not Chess960) castling rights/home pieces, empty path and current/transit/destination king attack against explicit FEN; complete game history is not inferred.
Description
Standard chess castling needs rights, an empty path and safe king start/transit/destination squares.
Standard chess castling needs rights, an empty path and safe king start/transit/destination squares. Queenside also needs an empty b-file square.1
Enter supported FEN and king/queen side. Validate required home king/rook, current check and standard path; simulate king transit to reject attacked squares. Return legality.
When to use Castling Rights Checker
Use Castling Rights Checker when you need to evaluate the supplied records under the calculation and evidence rules below. Chess 960, historical right reconstruction and broader move generation are excluded.
Prepare the supplied game state, observations and explicit variant settings. Follow the card, board, coordinate and state conventions in the calculation rules.
How to use Castling Rights Checker and understand its results
- Prepare the supplied game state, observations and explicit variant settings. Follow the card, board, coordinate and state conventions in the calculation rules.
- Enter positionFen, requestedCastlingSide using the field table and calculation rules, then run the tool.
- Read legalStandardCastling. The explanation below defines the units, signs, ordering and any flags or placeholder values.
- If the tool reports an input issue, correct the values and run it again. Apply the stated assumptions when interpreting a successfully returned result.
| Input field | Meaning | Value type; see rules below | Requirement |
|---|---|---|---|
| positionFen | Position fen | string | Required |
| requestedCastlingSide | Requested castling side | string | Required |
Enter supported FEN and king/queen side. Validate required home king/rook, current check and standard path; simulate king transit to reject attacked squares. Return legality.
legal=right and empty path and unattacked king route Units, indexing, boundary conditions and exceptional cases are defined in the calculation rules above.
| Output field | Meaning | Value type |
|---|---|---|
| legalStandardCastling | Legal standard castling | boolean |
{
"input": {
"positionFen": "r3k2r/8/8/8/8/8/8/R3K2R w KQkq - 0 1",
"requestedCastlingSide": "king"
},
"output": {
"legalStandardCastling": true
}
}Limitations and assumptions
Chess 960, historical right reconstruction and broader move generation are excluded.
Numeric inputs, where present, must be finite. Follow the calculation-specific rules for overflow, underflow and exceptional cases. Extremely large text inputs are rejected. Missing required fields, extra fields, wrong value types and violations of the calculation rules are input errors. A successfully returned false flag is an evaluated outcome; its meaning is explained above.
Alternative or Complementary methods
Use En Passant Legality Checker: Legal en passant requires the FEN target and a pawn capture that leaves the moving king safe. Removing the captured pawn can uncover a line attack. For a complementary task, use Threefold Repetition Counter: Chess repetition compares position identity while ignoring move clocks. An en-passant target changes identity only when a legal capture exists.
References
-
Castling Rights Checker — tool.io
Similar or alternative tools
- En Passant Legality Checker
Legal en passant requires the FEN target and a pawn capture that leaves the moving king safe. Removing the captured pawn can uncover a line attack.
- Threefold Repetition Counter
Chess repetition compares position identity while ignoring move clocks. An en-passant target changes identity only when a legal capture exists.