Which first move leads to which ECO volume

The first move decides the volume more than anything else. In the list behind this site, 1.e4 sends 2,027 of its 2,032 lines to volumes B and C, 1.d4 spreads over all five volumes with most lines in D, and 15 of the 20 first moves found in the list lead only to volume A.

Twenty first moves

White has twenty legal first moves, and every one of them appears in the list at least once. The spread is very uneven. The four best-known moves, 1.e4, 1.d4, 1.c4 and 1.Nf3, account for 3,676 of the 3,865 lines; the other sixteen share 189.

1.e42,032A 5, B 779, C 1248
1.d41,333A 329, B 2, C 1, D 636, E 365
1.c4202A 198, D 3, E 1
1.Nf3109A 103, D 5, E 1
1.Nc329A 29
1.b427A 27
1.f427A 27
1.g321A 21
1.g420A 20
1.b315A 15
1.h49A 9
1.a47A 7
1.e36A 6
1.f36A 5, C 1
1.a35A 5
1.d35A 5
1.h34A 4
1.Na34A 4
1.Nh33A 3
1.c31A 1

Named lines by White’s first move, with the volumes they are filed in (letter and number of lines).

1.e4: two volumes and a handful of strays

Of the 2,032 lines that start 1.e4, 1,248 are in volume C and 779 in volume B. Black’s first reply decides which. After 1...e5 or 1...e6 the line goes to C; most other replies go to B. The five lines that start 1.e4 but are filed in volume A are exceptions: Zukertort Opening: Tennison Gambit; Zukertort Opening: Tennison Gambit, Brigg’s Trap; King’s Indian Attack: Sicilian Variation; Benoni Defense: French Benoni; Rat Defense: Balogh Defense.

Every one of the 100 codes in volume B and in volume C holds at least one 1.e4 line. The biggest single 1.e4 code is B00, with 83 lines.

1.d4: the widest reach

1.d4 is the only first move that reaches all five volumes. It has 636 lines in D, 365 in E and 329 in A, with 2 in B and 1 in C. The split again depends on Black. Counting lines by volume: after 1...d5, 461 D, 1 E; after 1...Nf6, 363 E, 174 A, 172 D; after 1...f5, 70 A.

1.c4 and 1.Nf3

The English Opening, 1.c4, has 202 lines, 198 of them in volume A. 1.Nf3 has 109, again mostly in A (103). The few lines of either move that carry D or E codes are ones whose final position belongs to a queen’s pawn opening. After 1.c4 the commonest replies in the list are 1...e5 (59), 1...Nf6 (45), 1...e6 (40); after 1.Nf3 they are 1...d5 (52), 1...Nf6 (25), 1...c5 (6).

The rare first moves

The remaining sixteen first moves have between 1 and 29 lines each, and 15 of them are found only in volume A. Most sit under A00, the code for uncommon first moves, which is why that code holds 144 lines, more than any other. 1.Nc3 (29 lines), 1.b4 and 1.f4 (27 each) are the most developed of them in the list; 1.c3 appears once.

A first move with many lines in the list is not necessarily a strong or popular move. The count only shows how many named branches people have catalogued. 1.g4, for example, has 20 named lines.

How many codes each first move reaches

Counting codes rather than lines gives a different view. 1.e4 lines are filed under 204 different codes and 1.d4 lines under 263; 1.c4 reaches 36 codes and 1.Nf3 15. Of the sixteen remaining first moves, 12 are confined to a single code. Every one of the twenty first moves is a named position in its own right, so even a game that stops after White’s first move has a name and a code.

Black’s answers decide the rest

Once White’s first move is known, Black’s reply does most of the remaining sorting. The table counts the commonest replies to the two main first moves among the lines that go on past move one.

Reply	Lines after 1.e4	Reply	Lines after 1.d4
1...e5	1033	1...Nf6	709
1...c5	410	1...d5	462
1...e6	214	1...f5	70
1...c6	110	1...g6	22
1...Nf6	56	1...c5	19
1...d5	48	1...e5	16

After 1.e4 the replies 1...e5, 1...c5 and 1...e6 carry most of the named lines; after 1.d4 the field is led by 1...d5 and 1...Nf6. Each of these replies then has its own range of codes, which is why a code page shows the road of named positions that leads to it, starting from the first move.

Reading a code from the first move

If you know only the first move of a game, you can usually narrow it to one or two volumes. 1.e4 means B or C; 1.d4 means D, E or A; anything else almost certainly means A. To go further you need Black’s reply and often several more moves. The opening finder does this for a whole sequence, and its starting screen lists the same twenty first moves with the named position each one reaches at once.

Sources

Opening names and move sequences: lichess-org/chess-openings (CC0), retrieved 2026-10-28. All counts replayed and computed by ecocodes with python-chess; definitions on How to read a code page.