Irregular chess opening

Irregular openings are chess openings with an unusual or rare first move by White. These openings are:

• 1.a3 - Anderssen's Opening
• 1.a4 - Ware Opening
• 1.b4 - Sokolsky Opening, also known as Polish or Orangutan Opening
• 1.c3 - Saragossa Opening
• 1.d3 - Mieses Opening
• 1.e3 - Van 't Kruijs Opening
• 1.f3 - Barnes Opening, also known as Gedult's Opening
• 1.g4 - Grob's Attack
• 1.h3 - Clemenz Opening, or Basman's Attack
• 1.h4 - Desprez Opening, or Kadas Opening
• 1.Na3 - Durkin Opening, also known as Durkin's Attack or the Sodium Attack
• 1.Nc3 - Dunst Opening
• 1.Nh3 - Amar Opening, also known as Paris Opening

The above openings are all categorized under the ECO code A00. Openings that are not "irregular" comprise:

• 1.e4 - King's Pawn Game
• 1.d4 - Queen's Pawn Game
• 1.c4 - English Opening
• 1.Nf3 - Réti Opening or Zukertort Opening
• 1.f4 - Bird's Opening
• 1.g3 - Benko's Opening
• 1.b3 - Larsen's Opening

If White plays a regular opening and Black responds in an unconventional way, the opening is not categorized A00. For instance, 1.e4 a6 is classified as B00 (King's Pawn Game).

Read more:

• Open Game - 1.e4 e5
• Semi-Open Game - 1.e4 other
• Closed Game - 1.d4 d5
• Semi-Closed Game - 1.d4 other
• Flank opening - 1.c4, 1.Nf3, 1.f4, and others
• List of chess openings
• Encyclopaedia of Chess Openings