Budapest Gambit Accepted, Main Line

After 3...Ng4 the knight escapes the tempo gained by 3. dxe5 and goes straight for e5. White can return the pawn for space or development, or try to keep it at some positional cost. Engines give White a slight edge, and Lichess results are close to level. The most common reply is 4. Nf3, the Adler Variation. There 4...Bc5 forces 5. e3 to cover f2, which shuts in the queen's bishop. Without Bf4 White lacks defenders, and Black recovers the pawn, as in 5...Nc6 6. Nc3 O-O 7. Be2 Re8 8. O-O Ngxe5 9. Nxe5 Nxe5. Black often follows with a rook lift through ...a5, ...Ra6 and ...Rh6.

The Rubinstein Variation, 4. Bf4, scores better for White. After 4...Nc6 5. Nf3 Bb4+, White chooses between 6. Nc3, which risks doubled isolated c-pawns after 6...Bxc3+ 7. bxc3, and 6. Nd2, after which 6...Qe7 wins the pawn back. In that line, 7. a3 Ngxe5 8. axb4?? runs into 8...Nd3#. The Alekhine Variation, 4. e4, gives up the pawn at once: 4...Nxe5 5. f4 builds a broad center, and Black answers with 5...Nec6 or 5...Ng6.