Open

The Open Variation, also called the Open Defense or Open Spanish, is Black's main alternative to the Closed systems. Instead of 5...Be7, Black captures on e4. The aim is not to keep the pawn but to use the moves White spends winning it back to gain a foothold in the center, at the risk of opening the e-file while the black king is still uncastled. The main line is 6. d4 b5 7. Bb3 d5 8. dxe5 Be6. The bishop move is close to forced, because it guards d5 and develops at the same time. White then chooses among 9. c3, 9. Nbd2 (the Bernstein Variation) and 9. Qe2 (the Howell Attack). After 9. c3, Black has the Classical 9...Be7, the Italian 9...Bc5 and the Berlin 9...Nc5. The Riga Variation, 6...exd4, is considered dubious because Re1 exploits the open e-file. In online play, 6. Re1 is nearly as common as 6. d4. After 6. Re1, the reply 6...Nc5 7. Bxc6 dxc6 gives Black comfortable play.

The earliest recorded game in the line was won by Johann Löwenthal in 1854. Viktor Korchnoi chose it against Anatoly Karpov in their 1978 and 1981 world championship matches. Engines rate the position as roughly balanced.