What is the difference between a developing move and an attacking move?
These answers restate the rules implemented by our open-source engine, which follows the WXF laws for movement, checkmate and both repetition rulings: a side that forces a repetition by perpetual check or perpetual chase loses rather than drawing. The chase half has not been validated against the official casebook. Where an answer refers to a specific position, that position lives on the linked reference page, where the build verifies it before publishing.
Direct answer
A developing move improves a piece without forcing a reply; an attacking move creates a threat the opponent must answer. Both are necessary, but confusing one for the other is a common cause of a lost opening: playing developing moves while believing you are attacking gives the opponent free time to catch up.
Why the distinction matters
A move can look aggressive, sliding a chariot forward, and still not actually threaten anything the opponent has to answer. If nothing forces a reply, it is development dressed up as an attack, and the opponent is free to keep developing themselves.
The strongest moves do both
A move that develops a piece and creates a genuine threat at the same time is the most efficient kind available, which is exactly why Screen Horses is so highly regarded as a reply to the Central Cannon: it defends and develops in the same motion.
Related questions
How do I tell if a threat is real?
Ask whether the opponent must spend a move dealing with it, or whether ignoring it costs nothing concrete.
Is it bad to play purely developing moves?
Not early on, when there is nothing to attack yet. It becomes a problem once a real target exists and you are still just developing.
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