FEN記法とは何ですか？

Forsyth–Edwards Notation（FEN）は1行のテキストでチェスのポジションを記述する標準テキスト形式です。StockfishなどのチェスエンジンやLichess、Chess.comなどのウェブサイトで使用されています。

ツールはチェスのルールを適用しますか？

いいえ。これはポジション設定ヘルパーであり、ゲームエンジンではありません。どこにでも駒を配置できます。動きのハイライトは典型的な動きのパターンを示しますが、特定のゲーム状態における合法性を検証するものではありません。

パズルを設定するために使用できますか？

はい。ポジションを設定し、FENをエクスポートし、お気に入りのチェスアプリやエンジンに貼り付けてパズルを分析または解いてください。

ハイライトされたマスは何を意味しますか？

ボード上の駒をクリックすると、ツールはその駒の種類が他の駒を無視して標準的な動きのパターンに基づいて移動できる可能性のあるすべてのマスをハイライトします。

fun 無料サインアップ不要

チェスボードセットアップヘルパー

インタラクティブなボードで任意のチェスポジションを設定し、FEN記法をエクスポートまたはインポートし、駒の動きをハイライトします。

ツールを読み込み中…

このツールについて

座標ラベルa〜hと1〜8が付いたインタラクティブな8×8ボードでチェスの駒を配置、移動、削除できます。パレットから任意の駒を選択し、マスをクリックして配置し、駒が置かれたマスをクリックしてその駒が移動できる場所をハイライトします。チェスエンジンで使用するためのFEN記法としてポジションをエクスポートするか、FEN文字列をインポートして任意のポジションを即座に読み込めます。

使い方

1 「スタートにリセット」をクリックして標準の開始ポジションを読み込むか、「ボードをクリア」をクリックして空白のボードにしてください。
2 パレットから駒を選択してください（白または黒、キングからポーンまで）。
3 任意の空のマスをクリックして選択した駒を配置し、駒が置かれたマスをクリックして動きのハイライトを表示するか削除を切り替えてください。
4 「FENをエクスポート」をクリックしてポジションをクリップボードにコピーするか、FEN文字列を貼り付けて「FENをインポート」をクリックして読み込んでください。

What this tool is for — and what it deliberately is not

This is a position editor, not a chess engine. Its job is to let you build any arrangement of pieces on an 8×8 board and turn that arrangement into FEN — the standard text string that chess software reads — or to take a FEN string and rebuild the position visually. It does not enforce the rules of chess. You can place two white kings, stack pawns on the back rank, or set up a position that could never arise in a real game. That freedom is the point: it makes the tool ideal for composing puzzles, diagramming a lesson, or capturing a position from a book.

How FEN actually encodes a board

Forsyth–Edwards Notation describes a whole position in a single line. The first and longest part is the piece placement, read rank by rank from the 8th rank (Black's back row) down to the 1st, with ranks separated by /. Within each rank, an uppercase letter is a White piece and a lowercase letter is a Black piece — K/k king, Q/q queen, R/r rook, B/b bishop, N/n knight, P/p pawn — and a digit means that many consecutive empty squares. So 8 is an empty rank and 4P3 means four empties, a white pawn, then three empties.

The standard starting position is rnbqkbnr/pppppppp/8/8/8/8/PPPPPPPP/RNBQKBNR w KQkq - 0 1. The trailing fields after the board describe whose turn it is, castling rights, the en passant square, and the move counters. This editor focuses on the board itself: when you export, it writes the piece layout you built and fills the remaining fields with a neutral default of w - - 0 1 (White to move, no castling rights recorded, no en passant, fresh counters). If you need specific side-to-move or castling data, edit those trailing fields by hand after exporting.

A worked example

Start from a blank board. Select the white king from the palette and click e1. Select the black king and click e8. Select a white pawn and click e4. Press Export FEN and you get a string whose board section is 4k3/8/8/8/4P3/8/8/4K3, followed by w - - 0 1. Read it back to check your understanding: rank 8 is 4k3 (four empties, the black king on e8, three empties), the pawn rank 4 is 4P3, and rank 1 is 4K3 with the white king on e1. Copy that line into Lichess's board editor or paste it into Stockfish, and the exact position appears.

Movement hints, and their honest limits

Click a piece already on the board and the tool highlights every square that piece type could reach by its geometry — a rook's ranks and files, a bishop's diagonals, a knight's L-shapes, the king's eight neighbours, a pawn's forward and capture squares. This is a teaching aid for showing how each piece moves. It is purely geometric: the highlights ignore other pieces entirely, so they do not stop at a blocker, they do not exclude moving into check, and they do not validate legality for the current game state. Treat them as "where this kind of piece moves on an empty board," not as "the legal moves available right now."

Genuine use cases

Setting up puzzles and studies. Build the position once, export the FEN, and load it into any analysis engine to solve or verify a tactic.
Transcribing a position from a book or photo. Recreate the diagram by clicking pieces into place, then export a FEN you can analyse on a computer.
Teaching beginners. Use Reset to Start, then drag the lesson forward; use the movement highlights to show a new player exactly how a knight or bishop travels.
Sharing a position. FEN is plain text, so a single line of it can be pasted into a chat, an email, or a forum post and reconstructed perfectly by the reader.

Tips and common mistakes

Clicking an occupied square does not replace the piece. A first click on an occupied square selects it and shows movement hints; clicking it again deselects. To take a piece off, switch on Eraser mode and click it. To swap pieces, erase first, then place.
FEN reads top-down, board reads bottom-up. The first group in a FEN string is rank 8 (Black's side), which trips up newcomers who expect it to start from White. The on-board coordinate labels (a–h, 1–8) help you keep oriented.
Imported strings only need a valid board section. If an import fails, the most common culprit is a malformed piece-placement field — wrong letters, ranks that do not add up to eight squares, or the wrong number of / separators.
Remember the missing metadata on export. Because side-to-move and castling default to a neutral value, an engine analysing your exported position assumes White moves next and no castling is available. Set those fields yourself if they matter to the analysis.

Privacy note

Everything happens in your browser. Building the board, generating FEN, and parsing an imported string are all done locally in JavaScript — no position is sent to a server. You can work entirely offline.