Lichess/chess-openings

Dataset Card for Lichess Puzzles

Dataset Description

3704 chess openings with their Encyclopaedia of Chess Openings (ECO) classification.

Dataset Creation

Creating this dataset is detailed in its original GitHub repository.

Updates to the original repo will also be reflected in this version. Dataset last updated on May 20th, 2026.

Dataset Usage

Using the datasets library:

from datasets import load_dataset

dset = load_dataset("Lichess/chess-openings", split="train")

Using the pandas library:

import pandas as pd

df = pd.read_parquet("hf://datasets/Lichess/chess-openings/data/train-00000-of-00001.parquet")

Using the polars library:

import polars as pl

df = pl.read_parquet('hf://datasets/Lichess/chess-openings/data/train-00000-of-00001.parquet')

Dataset Details

Dataset Sample

One row of the dataset looks like this:

{
 'eco-volume': 'B',
 'eco': 'B31',
 'name': 'Sicilian Defense: Nyezhmetdinov-Rossolimo Attack, Fianchetto Variation, Totsky Attack',
 'pgn': '1. e4 c5 2. Nf3 Nc6 3. Bb5 g6 4. O-O Bg7 5. c3 Nf6 6. Qa4',
 'uci': 'e2e4 c7c5 g1f3 b8c6 f1b5 g7g6 e1g1 f8g7 c2c3 g8f6 d1a4',
 'epd': 'r1bqk2r/pp1pppbp/2n2np1/1Bp5/Q3P3/2P2N2/PP1P1PPP/RNB2RK1 b kq -'}
}

Dataset Fields

Every row of the dataset contains the following fields:

• eco-volume: string, the ECO parent category. Can be either A, B, C, D, or E.
• eco: string, the ECO.
• name: string, the name of the opening in English.
• pgn: int, the sequence of moves leading to the opening position. If not unique, the moves are the most common ones leading to that opening.
• uci: int, the same moves described by the pgn field in UCI notation.
• epd: int, the EPD (FEN without move numbers) of the opening position, en passant field only if legal

Dataset Conventions

• Title case is used for opening names.
• Names are structured like Opening family: Variation, Subvariation, ..., e.g., Sicilian Defense: Najdorf Variation, English Attack.
• The suggested way to classify games is to play moves backwards until a named position is found. To make this work well with common transpositions, multiple entries for a single opening may be added.
• However, each name has a unique shortest line. If necessary, a distinguishing move is appended, e.g., King's Gambit Accepted: Schurig Gambit, with Bb5.

Additional Information

• To contribute to the dataset, send a PR on the dataset's GitHub repository.