HEN (Hemme Notation)

HEN (Hemme Notation) is a lightweight, text-based format designed for efficiently encoding and sharing Go board positions.

Inspired by the Forsyth-Edwards Notation (FEN) used in chess, HEN allows developers and players to represent the goban state — including board dimensions, stone placement, the Ko situation, and whose turn it is — in a reasonably compressed yet human-readable string.

Why HEN?

While SGF (Smart Game Format) is the absolute standard for recording complete Go games and complex variations (move trees), it is not ideal for representing a single, static board position. SGF files can be verbose and are not easily embeddable.

HEN fills this gap by providing a compact, snapshot-based format representing a single state of the game. This makes it perfect for:

• Sharing specific board positions via URLs, query parameters, or chat messages.
• Indexing databases of Tsumego (Go problems) or specific board states.
• Writing concise, readable unit tests for Go applications and bots.
• Embedding board states in documentation without the overhead of full SGF trees.

Structure

A HEN string is composed of parts A through G. All parts are optional and may appear in any order. Whitespace, newlines, and tabs are completely ignored: a HEN string can exist on a single line or span multiple lines by breaking between parts.

A. Indicate the goban size: .{number}x{number} - e.g.: .19x19

B. Indicate the goban content: _{goban} - e.g. _19bwb2w3_10Kb_1Cw3bNwbb

C. Indicate if there is a ko: .{letter}{number} - e.g. .L7

D. Indicate the last move:

• Placement: .{letter}{number}{stone} - e.g. .K7w
• Pass: .p{stone} - e.g. .pw

E. Indicate whose turn it is: .{stone} - e.g.: .b

F. Indicate a label: .{letter}{number}-{label} - e.g.: .K10-a

G. Indicate a symbol: .{letter}{number}-{mark} - e.g.: .K10-X

Goban content

The content of the goban is constructed by observing the board from Black's side and proceeding one row at a time, from top to bottom. If a row contains stones, write:

_{number} - e.g., in a 19x19 goban, the topmost row will be: _19

Indicate the column letter (uppercase) of the first stone in that row, followed by its color. For each subsequent adjacent stone, only the color is needed — the column is inferred from the sequence:

_{number}{letter}{stone...} - e.g.: _19Abwbbwww

The column letter A may be omitted when the first stone is in column A; e.g. _19Ab is equivalent to _19b.

The {stone}{number} form can be used to encode consecutive runs of the same color; e.g. _19bwbbwww is equivalent to _19bwb2w3.

Repeat for each row containing at least 1 stone.

Formats

{number}: integer > 0. Leading zero is allowed.

{letter}: an uppercase alphabetic letter except I.

{stone}: a lowercase letter indicating the color:

• b: Black
• w: White

For multi-color Go, you can also use:

• r: Red
• g: Green
• l: Blue
• y: Yellow
• p: Purple

{label}: a simple text (typically a letter or a number).

{mark}: can be CR, SQ, TR, MA (respectively for: circle, square, triangle, X)

Examples

1) An arbitrary position

Single line: .19x19_19bwb2w3_10Kb_8Kbw_7JbwMw_6Kbw_1Cw3bNwb2.L7.K7w.b

Multiple lines:

.19x19
_19 bwb2w3
_10 Kb
_08 Kbw
_07 JbwMw
_06 Kbw
_01 Cw3bNwb2
.L7
.K7w
.b

Equivalent SGF:

(;GM[1]FF[4]SZ[19]PB[Black]PW[White]
;AB[aa][ca][da][jj][jl][im][km][jn][fs][ns][os]AW[ba][ea][fa][ga][kl][lm][kn][cs][ds][es][ms]
;W[jm])

2) The famous Ear-reddening move

The following HEN (241 characters) represents the goban position of the famous Ear-reddening Game, played in 1846 by Shusaku against Gennan Inseki, immediately after the eponymous move. The marks are as shown in the Sensei's Library article about the game:

_19Kbw2_18DbKbwNwPw2b_17Cw2FbJwb2w2Pwb_16Mb3Rb_15LbQb2_14Qbw2_13Ow3b3_12Pbw3b_11KbNbw2b3_10Nw2bRbw_9CwPwb2w_8Pwbwb_7NwPwbw2_6CwKbMbwPwb_5GbJwMbwbwbw_4CbEbHbMbw2bRw_3FbwbwLw2b4w2_2GbwKw2Nwb2Rbw_1JwMwObQbSb.K11b.w.M6-SQ.M5-SQ.M4-SQ.K6-SQ.J5-CR

Multiple lines (for clarity / during manual entry):

_19 Kbw2
_18 DbKbwNwPw2b
_17 Cw2FbJwb2w2Pwb
_16 Mb3Rb_15LbQb2
_14 Qbw2_13Ow3b3
_12 Pbw3b
_11 KbNbw2b3
_10 Nw2bRbw
_09 CwPwb2w
_08 Pwbwb
_07 NwPwbw2
_06 CwKbMbwPwb
_05 GbJwMbwbwbw
_04 CbEbHbMbw2bRw
_03 FbwbwLw2b4w2
_02 GbwKw2Nwb2Rbw
_01 JwMwObQbSb
.K11b.w
.M6-SQ.M5-SQ.M4-SQ.K6-SQ.J5-CR

Equivalent SGF (521 characters):

(;GM[1]FF[4]CA[UTF-8]SZ[19]
;AB[ja][db][jb][qb][fc][jc][kc][pc][ld][md][nd][qd][ke][pe][qe][pf][qg][rg][sg][oh][sh][mi][pi][qi][ri][oj][qj][pk][qk][pl][rl][pm][jn][ln][pn][go][lo][no][po][cp][ep][hp][lp][op][fq][hq][mq][nq][oq][pq][gr][nr][or][qr][ns][ps][rs]AW[ka][la][kb][mb][ob][pb][cc][dc][ic][lc][mc][oc][qf][rf][ng][og][pg][ph][qh][rh][ni][oi][mj][nj][rj][ck][ok][rk][ol][ql][mm][om][qm][rm][cn][mn][on][io][mo][oo][qo][mp][np][qp][gq][iq][kq][lq][qq][rq][hr][jr][kr][mr][rr][is][ls]
;B[ji]SQ[ln][lo][lp][jn]CR[io])

Equivalent URL-encoded SGF (1031 characters):

%28%3BGM%5B1%5DFF%5B4%5DCA%5BUTF-8%5DSZ%5B19%5D%0A%3BAB%5Bja%5D%5Bdb%5D%5Bjb%5D%5Bqb%5D%5Bfc%5D%5Bjc%5D%5Bkc%5D%5Bpc%5D%5Bld%5D%5Bmd%5D%5Bnd%5D%5Bqd%5D%5Bke%5D%5Bpe%5D%5Bqe%5D%5Bpf%5D%5Bqg%5D%5Brg%5D%5Bsg%5D%5Boh%5D%5Bsh%5D%5Bmi%5D%5Bpi%5D%5Bqi%5D%5Bri%5D%5Boj%5D%5Bqj%5D%5Bpk%5D%5Bqk%5D%5Bpl%5D%5Brl%5D%5Bpm%5D%5Bjn%5D%5Bln%5D%5Bpn%5D%5Bgo%5D%5Blo%5D%5Bno%5D%5Bpo%5D%5Bcp%5D%5Bep%5D%5Bhp%5D%5Blp%5D%5Bop%5D%5Bfq%5D%5Bhq%5D%5Bmq%5D%5Bnq%5D%5Boq%5D%5Bpq%5D%5Bgr%5D%5Bnr%5D%5Bor%5D%5Bqr%5D%5Bns%5D%5Bps%5D%5Brs%5DAW%5Bka%5D%5Bla%5D%5Bkb%5D%5Bmb%5D%5Bob%5D%5Bpb%5D%5Bcc%5D%5Bdc%5D%5Bic%5D%5Blc%5D%5Bmc%5D%5Boc%5D%5Bqf%5D%5Brf%5D%5Bng%5D%5Bog%5D%5Bpg%5D%5Bph%5D%5Bqh%5D%5Brh%5D%5Bni%5D%5Boi%5D%5Bmj%5D%5Bnj%5D%5Brj%5D%5Bck%5D%5Bok%5D%5Brk%5D%5Bol%5D%5Bql%5D%5Bmm%5D%5Bom%5D%5Bqm%5D%5Brm%5D%5Bcn%5D%5Bmn%5D%5Bon%5D%5Bio%5D%5Bmo%5D%5Boo%5D%5Bqo%5D%5Bmp%5D%5Bnp%5D%5Bqp%5D%5Bgq%5D%5Biq%5D%5Bkq%5D%5Blq%5D%5Bqq%5D%5Brq%5D%5Bhr%5D%5Bjr%5D%5Bkr%5D%5Bmr%5D%5Brr%5D%5Bis%5D%5Bls%5D%0A%3BB%5Bji%5DSQ%5Bln%5D%5Blo%5D%5Blp%5D%5Bjn%5DCR%5Bio%5D%29