NIC-Key

An opening is the early phase of a game and is commonly studied as families of related move sequences. NIC-Key is a taxonomy, a system for organizing and naming those openings. NIC refers to New In Chess. Its letters commonly derive from English opening names: SI identifies the Sicilian Defence and KI the King's Indian Defence. Number groups then distinguish variations and subvariations more precisely.

The code describes where a sequence belongs within opening theory. It is not a move, an evaluation, or a recommendation. Nearby positions can receive different codes when they belong to separate theoretical branches, while one broad opening family can be divided among many codes.

NIC-Key and ECO, the Encyclopedia of Chess Openings classification, are parallel systems. They can be mapped, but their divisions do not necessarily match exactly. FICS, for example, can display both codes for a game and answer queries that translate between them.

In structured data, a NIC code can be stored as descriptive data in a PGN tag pair, where PGN means Portable Game Notation, or through the nic opcode, meaning the operation name that identifies that data, inside an EPD operation, where EPD means Extended Position Description. In either case, the code classifies the associated opening; it does not alter the position or the legality of moves.