Shogi Notation for Chess Players: KIF, USI and SFEN

For a chess player, the rules of shogi are the easy part. What takes longer is reading a position — and the reason is not the kanji. It is that a shogi position has a part that is not on the board.

In chess you read a position by scanning the 64 squares. In shogi that is only half the picture. Every piece you capture goes into your hand, and on a later turn you can drop it onto almost any empty square. Two positions with identical boards can be completely different games depending on what each side is holding. A quiet-looking board can hide a forced sequence that starts with a drop. So the first habit to build is: read the hands before you read the board.

Everything else in this article follows from that one idea. It maps shogi notation — the coordinates, the machine form (USI) and the position string (SFEN) — onto what you already know from chess, using the same conventions the notation engine in Ponder (our chess and shogi study board) uses when it reads a file. If you want the practical side instead (what a .kif file looks like and what 同 成 不成 打 mean in the move list), see the companion article How to Read a Shogi KIF File.

Coordinates: files go right to left

A shogi board is 9×9. Squares are named file first, then rank, as in chess. The difference:

• Files are numbered 1 to 9 from right to left, from the perspective of the player who moves first.
• Ranks are numbered 1 to 9 from top to bottom, again from that player's side. In Japanese notation ranks are written with kanji numerals (一 二 三 … 九); in USI they are letters a to i.

So the square a chess player would instinctively call "a1" (bottom-left) is 9-9 in shogi. The bottom-right corner is 1-9. The top-left corner, from the first player's view, is 9-1.

If you remember one thing: file 1 is on the right.

Who moves first: Sente is Black

The player who moves first is Sente; the second player is Gote. In English writing Sente is commonly called "Black" and Gote "White" — the opposite of chess, where White moves first. Records mark Sente's moves with ☗ (or ▲) and Gote's with ☖ (or △).

Our engine describes the side to move as Sente (Black) and Gote (White) so both names stay visible. When a shogi position string says b, it means Sente to move.

Move numbers count every half-move

In PGN, 12. O-O-O is White's twelfth move and the game has reached ply 23. In shogi records, every half-move gets its own number. Move 1 is Sente's first move, move 2 is Gote's reply, move 23 is Sente's twelfth move.

This is the single most useful thing to internalise, because it removes a whole class of off-by-one mistakes. In our engine's terms: for shogi, the record's move number and the ply count are identical.

Drops and promotion: the two rules with no chess equivalent

Drops. When you capture a piece in shogi, it becomes yours, and on a later turn you may place it on almost any empty square instead of moving a piece on the board. That is a drop. In Japanese notation it is marked with 打; in USI it is written with the piece letter and an asterisk, e.g. P*5e drops a pawn on 5-e. A drop has no origin square, which is why records treat it as a separate syntax.

Promotion. In chess, a pawn reaching the last rank must promote. In shogi, most pieces may promote when they move into, within, or out of the far three ranks, and promotion is usually optional. The record therefore has to state whether it happened (成 / 不成). In USI a promotion is a + appended to the move: 8h2b+.

USI: the coordinate form programs use

USI writes a normal move as origin square then destination square, with files as digits and ranks as letters:

7g7f

File 7, rank g (the seventh rank) to file 7, rank f. Compare chess's e2e4 from the UCI protocol; the shape is the same, only the rank axis is lettered and the file axis runs right to left. Our engine converts every parsed move into USI internally, and when an AI answer proposes a line, it is USI that gets validated against the rules before anything is shown on the board.

SFEN: FEN for shogi

The starting position in SFEN:

lnsgkgsnl/1r5b1/ppppppppp/9/9/9/PPPPPPPPP/1B5R1/LNSGKGSNL b - 1

If you know FEN, you can read this immediately:

• Ranks from top to bottom, separated by /, with digits for runs of empty squares. 9 is a whole empty rank.
• Lowercase is Gote's pieces (top of the board), uppercase is Sente's (bottom).
• Piece letters: p pawn, l lance, n knight, s silver, g gold, b bishop, r rook, k king. A promoted piece is written with a + in front, e.g. +P.
• b = Sente ("black") to move; w would be Gote.
• - = no pieces in hand. When pieces are in hand, they are listed here (for example 2Pb would mean Sente holds two pawns and Gote holds a bishop).
• 1 = the move number.

SFEN has no castling field and no en passant field, because neither rule exists in shogi. The "pieces in hand" field replaces them — and it matters far more, because a piece in hand is a piece that can appear anywhere next move.

Two habits from chess to unlearn

Scanning only the board. Said once more because it is the one that costs games: when you look at an SFEN, read the hand field before the board; when you look at a diagram, find where the captured pieces are shown. A rook in hand is a rook that can appear on any open file next move.

Counting moves in pairs. Move 24 in a shogi record is Gote's twelfth move, and asking "what happened at move 12" will land you on Gote's sixth. Read the number as a ply and the confusion disappears.

A quick reference

Once pieces in hand, the coordinates and the half-move numbering are in place, the rest is vocabulary. The interesting part of shogi — why a piece in hand is worth waiting for, why the same square gets contested three moves in a row — starts after that. If you want to see it rather than read it, the sample shogi games in Ponder are a good place to ask an AI "why this move?" and press the move to watch the board answer.