FEN vs PGN: Share a Position or a Complete Chess Game

The practical difference in FEN vs PGN is scope: FEN describes one chess position; PGN describes a game and its moves. Use FEN when you want someone to inspect a diagram. Use PGN when they need to replay how the position arose. A FEN alone cannot recover the earlier move history.

Use FEN for a snapshot

Here is the standard starting position:

rnbqkbnr/pppppppp/8/8/8/8/PPPPPPPP/RNBQKBNR w KQkq - 0 1

The six space-separated fields mean:

1. Piece placement: ranks from eight to one, separated by slashes. Uppercase letters are White’s pieces and lowercase letters are Black’s. A number counts consecutive empty squares.
2. Side to move: w for White or b for Black.
3. Castling rights: KQkq lists White’s kingside and queenside rights followed by Black’s. A dash means none.
4. En passant target: a square associated with the previous two-square pawn move, or a dash.
5. Half-move clock: plies since the most recent pawn move or capture.
6. Full-move number: starts at one and increases after Black moves.

Castling rights depend on the history, not simply whether the pieces currently occupy their original squares. Similarly, an en passant target must agree with the previous move. Some exporters omit an en passant target when no legal capture exists; the chess.js documentation explains that convention for the library used on this site.

Use the board editor to create a position and set those details. Its checks catch basic invalid setups, but do not prove every diagram is reachable through a legal game.

Use PGN for a sequence

PGN combines optional game headers with moves and a result. This unfinished study sequence can be replayed from the normal starting position:

[Event "Development study"]
[Result "*"]

1. e4 e5 2. Nf3 Nc6 3. Bc4 Bc5 *

The asterisk leaves the result unspecified. It does not declare a draw. A PGN starting from a custom position needs the appropriate SetUp and FEN headers so the first move is interpreted on the correct board.

Our analysis board retains moves and variations. It does not retain imported comments or annotation symbols when exporting. Keep the original PGN if those notes matter to you.

Choose the format for your task

| Task | Use | Reason | | --- | --- | --- | | Ask about a puzzle diagram | FEN | The recipient needs the position and side to move. | | Review where a game changed | PGN | Earlier moves and positions are essential. | | Share the position currently displayed | FEN link | It opens the board at that point. | | Preserve study variations | PGN | A move tree needs more than a snapshot. |

If the import fails

For FEN, count eight ranks and eight squares per rank, then check both kings, active color and special rights. For PGN, confirm you have one game, legal notation, and the correct starting position. A screenshot or a copied evaluation number is not PGN.

Move history can also affect draw detection, including repetition. Two studies with the same displayed board may have different histories. Use a complete game when those distinctions matter.

Review a PGN game, or set up a FEN position when you only need one diagram.