Latest 1.0
License MIT
Platforms ios 8.0


SwiftChess is a chess engine written in Swift.



  • Move validation
  • AI with three difficulty levels
  • Callbacks for check, checkmate and stalemate
  • Supports castling
  • Supports En Passent
  • Supports pawn promotion
  • Asyncronous AI move calculation

SwiftChess doesn’t provide any UI, just all of the logic required to create a chess game. The example project contains a complete UIKit UI with touch handling that you start from if you like.


The example application contains a complete implementation of SwiftChess.

Run Example/Example.xcodeproj

Basic Use

Start a game
// Make a human player
let whitePlayer = Human(color: .white)

// ... or an AI Player
let blackPlayer = AIPlayer(color: .black, configuration: AIConfiguration(difficulty: .hard))

// Create a game       
let game = Game(firstPlayer: whitePlayer, secondPlayer: blackPlayer)
Make a move
if let player = game.currentPlayer as? Human {

    let currentLocation = BoardLocation(x: 4, y: 1)
    let newLocation = BoardLocation(x: 4, y: 2)

    try! player.movePiece(from: currentLocation,
                        to: newLocation)
Tell the AI to make a move
if let player =  game.currentPlayer as? AIPlayer {
Then just wait for the callbacks!
extension GameViewController: GameDelegate {

    func gameDidMovePiece(game: Game, piece: Piece, toLocation: BoardLocation) {
        // Move piece on board

    func gameDidRemovePiece(game: Game, piece: Piece, location: BoardLocation) {
        // Remove piece from board 

    func gameDidTransformPiece(game: Game, piece: Piece, location: BoardLocation) {
        // A pawn was promoted!

    func gameWonByPlayer(game: Game, player: Player) {

    func gameEndedInStaleMate(game: Game) {

    func gameDidChangeCurrentPlayer(game: Game) {
        // Make another move        


The entire state of a SwiftChess game can be converted to and initialised from a Dictionary.

Get a snapshot of the current state:

let dictionary: [String: Any] = game.dictionaryRepresentation

Initialise a game with a previous snapshot:

let game = Game(dictionary: dictionary)

The returned dictionary stores all the information required to create a ‘save game’ feature. The player colors, AI difficulty, piece positions etc.

You can serialize this to JSON, save it to disk, send it over the network etc.

Other stuff

Make a castling move
if game.board.canColorCastle(color: .white, side: .kingSide) {
    player.performCastleMove(side: .kingSide)
Support pawn promotion
func promotedTypeForPawn(location: BoardLocation, 
                         player: Human, 
                         possiblePromotions: [Piece.PieceType], 
                         callback: @escaping (Piece.PieceType) -> Void) {

    // Show UI for the user to select one of the possible promotion types
    // then call the handler

    // ...or some games just promote to a queen


Follow me on twitter @SteveBarnegren


SwiftChess is available under the MIT license. See the LICENSE file for more info.

Latest podspec

    "name": "SwiftChess",
    "version": "1.0",
    "summary": "Chess engine written in Swift",
    "description": "Chess engine written in Swift, support player vs player, and player vs AI games.",
    "homepage": "",
    "license": {
        "type": "MIT",
        "file": "LICENSE"
    "authors": {
        "Steve Barnegren": "[email protected]"
    "source": {
        "git": "",
        "tag": "1.0"
    "social_media_url": "",
    "platforms": {
        "ios": "8.0"
    "source_files": "SwiftChess/Source/**/*"

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