Chess Openings Lab
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King's Knight Opening

The King's Knight Opening is 1.e4 e5 2.Nf3, developing a knight and attacking the e5 pawn at once. White wants fast development with Bb5 or Bc4 and a later d4, while Black must decide how to meet the threat: defend with ...Nc6 or ...d6, or counter with ...Nf6.

Moves
1.e4 e5 2.Nf3
ECO
C40
Engine
+0.33 · a slight edge for White (Stockfish 17.1, depth 20)
Played
17,984 games in our lichess sample
White scores
53.6%

Key ideas for both sides

White

  • Against ...Nc6, Bb5 is the engine's first choice, pinning down the defender of e5 in Ruy Lopez style.
  • Against the Petrov's ...Nf6, take with Nxe5, retreat after ...d6, and build with d4 and Bd3.
  • Against the Philidor's ...d6, push d4 at once and add c3 and Bd3 for a broad, stable center.
  • Punish weakening replies such as ...f6 or ...Bc5 by taking on e5 when the tactics allow it.

Black

  • ...Nc6 is the top engine move: it defends e5, develops and keeps every main open game available.
  • ...Nf6 counterattacks e4; after Nxe5 never copy with ...Nxe4 at once, play ...d6 first.
  • ...d6 with ...Nd7 and a ...g6 fianchetto gives a solid but cramped Philidor setup.
  • Gambits such as ...f5 or ...d5 exist, but they give White a free hand against e5.

Plans and pawn structure

This is the main crossroads of the open games, and the plans depend on Black's reply. After ...Nc6, White chooses between Bb5 pressure on the e5 defender and Bc4 aiming at f7, usually followed by c3 and d4. After ...Nf6, the center opens and both sides race to develop. After ...d6, White builds a big center with d4 and Black aims for ...Nd7, ...Bg7 and a well-timed ...exd4 or ...c5. Many short traps live here, so careful development matters more than early raids.

What the engine plays from here

Stockfish 17.1 at depth 20 rates the position +0.33: a slight edge for White. Its three top choices for Black:

  1. +0.33 2...Nc6 3.Bb5 a6 4.Ba4 Nf6 5.d4
  2. +0.43 2...Nf6 3.Nxe5 d6 4.Nf3 Nxe4 5.d4
  3. +0.58 2...d6 3.d4 Nd7 4.c3 g6 5.Bd3

Pawns, from White's side.

How it scores on lichess

17,984 rated lichess games reached this position; White scored 53.6%.

under 120055.3%
1200–159953.0%
1600–199951.7%
2000 and up54.0%

Light: White wins. Grey: draws. Dark: Black wins. About the sample.

Traps and pitfalls

Légal's Mate (White sets it)

White unpins the f3 knight with 5.Nxe5 and leaves the queen on d1 hanging. If Black grabs it with 5...Bxd1, three minor pieces deliver mate in two moves around the black king.

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The Légal's Mate explained

Blackburne Shilling Gambit trap (Black sets it)

Black leaves e5 hanging with 3...Nd4 and answers 4.Nxe5 with 4...Qg5, attacking the knight and g2. If White grabs f7 with 5.Nxf7, the queen wins the h1 rook and the game ends with a smothered knight mate on f3.

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The Blackburne Shilling Gambit trap explained

Where it goes next

How to play against it

As Black, defend e5 with ...Nc6 or counterattack with ...Nf6; both lead to sound positions. Avoid ...f6, which weakens the king, and ...Bc5 or ...c6, which leave e5 loose. Know the Petrov rule: after Nxe5, play ...d6 before taking on e4.

Questions

What are the moves of the King's Knight Opening?

The King's Knight Opening starts 1.e4 e5 2.Nf3. Its ECO code is C40.

Is the King's Knight Opening good for White?

Stockfish 17.1 rates the position +0.33 at depth 20, which is a slight edge for White. In 17,984 lichess games from our sample, White scored 53.6%. The main gateway to the open games, suiting players at every level who want quick development and clear central play.

What is the main idea of the King's Knight Opening?

White develops the knight with a direct threat to e5, forcing Black to choose a defense. The main replies are ...Nc6, the Petrov's ...Nf6 and the Philidor's ...d6, and each leads to a different family of open games.

What should Black play next?

The engine's first choice is Nc6, with Nf6 and d6 close behind. ...Nc6 defends e5 while developing, and the engine meets it with Bb5, the start of the Ruy Lopez.

Updated October 2026. Sources and method.