Alapin Gambit

The Alapin Gambit develops the dark-squared bishop at once and leaves the e4-pawn unprotected. Black usually takes it, and the engine favors that capture, giving Black a slight edge. White normally answers 3...dxe4 with 4. f3, though 4. Nd2 Nf6 5. f3 is also seen. After 4...exf3 5. Nxf3, White aims for Bd3, short castling and a queen transfer via e1 to the kingside. With the e-pawns gone, the bishop on d3 bears down on h7, and Black's French bishop on c8 cannot contest it. After 4...Nf6 5. fxe4 Nxe4 6. Bd3, the check 6...Qh4+ fails: 7. g3 Nxg3 8. Bf2 leaves the knight short of defenders.

Declining is also common. On 3...Nf6, White can push 4. e5. Against 3...c5, the line 4. exd5 cxd4 5. Qxd4 exd5 6. Nc3 Nc6 7. Qxd5 is thought to suit White. The gambit is a rarely played sideline. On Lichess, White scores slightly better than Black in it.