How to name an opening from a game’s moves
Read the game backwards until a named position appears.
To name an opening, play through the game’s moves and keep the last position that has a name in the reference list; that name and its ECO code describe the opening. The list behind this site was designed to be read this way, backwards from the latest position until a named one turns up, and the opening finder does it automatically for any sequence you type or play.
Why the deepest named position
An opening name is a label for a position, not for a game. A game that starts with the Najdorf and goes on for forty moves is still a Najdorf game, and if it follows a known branch of the Najdorf for a few more moves, it carries that more precise name. The deepest named position is therefore the most precise description available. Going deeper than the list is not possible: after the last named position, the game is simply in unnamed territory.
Three worked examples
| Moves played | Plies | Deepest named position | Reached at |
|---|---|---|---|
| 1.e4 c5 2.Nf3 d6 3.d4 cxd4 4.Nxd4 Nf6 5.Nc3 a6 6.Be3 e5 7.Nb3 Be6 8.f3 | 15 | B90 Sicilian Defense: Najdorf Variation, English Attack | 8.f3 |
| 1.Nf3 d5 2.d4 Nf6 3.c4 e6 4.Nc3 Be7 | 8 | D37 Queen’s Gambit Declined: Three Knights Variation | 4.Nc3 |
| 1.e4 e5 2.Nf3 Nc6 3.Bb5 a6 4.Ba4 Nf6 5.O-O Be7 6.Re1 b5 7.Bb3 d6 8.c3 O-O 9.h3 Nb8 10.d4 Nbd7 | 20 | C95 Ruy Lopez: Closed, Breyer Defense, Zaitsev Hybrid | 10...Nbd7 |
The first game is a Najdorf with 6.Be3. The finder follows it until 8.f3, the last move after which the position has a name, and reports B90. Here that is the last move of the sequence, so every move typed was on a named line.
The second game starts with 1.Nf3, but by move 4 it has reached the position the list calls Queen’s Gambit Declined: Three Knights Variation. Because positions are compared, not move orders, the name is found even though the list records it after 1.d4. This is a transposition, the subject of a separate note.
The third game is a long Ruy Lopez. It stays inside named territory for 20 plies, deeper than 96% of all lines in the list, and ends at C95.
When nothing matches
Every one of the twenty first moves is itself a named position, so as soon as one move has been played the finder has at least that name to report. What can happen is that a game leaves the named lines very early, after a second or third move that no line in the list contains. The finder then still reports the last named position, and shows where the moves left the list: from that point they appear in grey. Taking back moves one at a time shows how the name changes on the way back.
One position, one name
The method works because the list never gives two names to the same position. We checked all 3,865 end positions: no two lines finish on the same board with the same side to move and the same castling and en passant rights. So once the finder has found the deepest named position, there is exactly one name and one code to report. Different move orders may lead there, but they lead to that single entry.
Typing moves
The finder accepts standard algebraic notation as it appears in most score sheets and books. Move numbers are optional; both 1.e4 e5 2.Nf3 and e4 e5 Nf3 are read correctly. Castling can be written O-O or 0-0. Check and annotation marks (+, #, !, ?) are ignored. If a move cannot be read or is illegal in the position, the finder stops at that move, shows it in red and names the opening from the moves before it.
Playing moves on the board
You can also click a piece and then its destination square. After every move, the finder lists the legal moves that keep the game on a named line, together with the number of named lines that pass through the resulting position. From the starting position, all 20 first moves appear in the list, each one a named position.
What the answer does not tell you
The finder names positions; it does not judge them. It does not know how often a line is played, how it scores, or whether a move is good. The list records names and move sequences only, so this site makes no claims about strength or popularity. A name with many lines is simply a name that has been catalogued in detail.
Sharing a result
The finder writes your moves into the page address, so the address can be copied and opened elsewhere to show the same position and name. Each code page also has a button that opens its reference line in the finder, a quick way to continue from a known position.
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.