♞ Knight Boards

Free tool

Chess notation checker

Paste a game and this checks that every move is legal. It reads a bare move list (1. e4 e5 2. Nf3 Nc6) or a full PGN with headers, comments and variations — then stops at the first move that can't be played and tells you why. Step through the result on the board. Nothing to install, no account.

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What it checks

Every move is replayed on a real board by the same rules engine that referees games on this site, so it catches the things a spell-checker for notation cannot:

  • Illegal moves — a piece that can't reach the square, a move that leaves your own king in check, castling after the king has moved.
  • Ambiguous moves — if you write Rd1 when both rooks can get to d1, it tells you so and gives you the two moves you had to choose between, Rad1 or Rhd1. That rule is explained in full under disambiguation.
  • Unreadable moves — typos like Nf9 or a piece letter that doesn't exist.
  • How the game ended — checkmate, stalemate, the fifty-move rule, threefold repetition or insufficient material.

It is forgiving about how you write things. Move numbers are optional, castling can be O-O or 0-0, annotation marks like !? and ?? are ignored, and PGN comments {like this} and (variations) are skipped.

Common questions

How do I check if a chess move sequence is legal? +

Paste the moves into a notation checker and it replays them on a board, stopping at the first move that cannot legally be played. This tool accepts a bare move list like 1. e4 e5 2. Nf3 Nc6, or a full PGN with headers, comments and variations, and reports the first illegal move along with the reason.

Why does my chess notation say the move is ambiguous? +

A move is ambiguous when two identical pieces could both legally reach the same square, so the notation does not say which one moved. The fix is disambiguation: add the file the moving piece came from, such as Rad1 instead of Rd1, or the rank if both pieces share a file, such as R1d2.

What is a PGN file? +

PGN stands for Portable Game Notation, the standard format for storing chess games in a file. It is ordinary algebraic notation plus a header of tags such as White, Black, Date and Result, so that software can read it. This checker accepts PGN with or without those headers.

Keep learning chess

How to read chess notation The whole system explained in order, from square names to full game scores. Chess notation symbols Every symbol in one table — x, +, #, ++, O-O and the annotation marks. Basic checkmate patterns Back-rank, ladder and scholar's mate — learn to finish winning games. How to play chess Board setup, every piece's moves and the special rules — a complete beginner's guide.

Now play one of your own.

Start a free game with a friend and the move list writes itself — valid notation, every time.

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