h6 as a prophylactic move in the opening As a low rated player myself, I often see people play h6 as black before playing Nf6, presumably to stop pins on g5 and things like the Fried Liver. Example:

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1. e4 e5 2. Nf3 Nc6 3. Bc4 h6?!


I keep hearing that such moves are an unnecessary waste of time, which would be better spent developing pieces.

Is h6 to allow the Knight to move to f6 justified? Should I be developing it to f6 at all?
The thing with h6 is that, in the opening, the move has one purpose for Black: prevent White from placing a piece on g5.

The drawbacks of the move are that:


It's a tempo investment. Tempos are important not to waste in, for example, open positions, where it is good to get your pieces out to active squares as early as possible.
It potentially weakens your kingside if you decide to castle short. A pawn on h6 can become a target for a piece sacrifice if White decides to launch a kingside attack.


So basically, you shouldn't make the move h6 out of habit. It should be played after carefully considering the consequences of letting an enemy piece reach g5. Does White even want to play a light piece to g5? If not, then why waste the tempo?

This of course applies to the pawn push h3 in the opening for White, and also in some sense the pawn pushes a3 and a6, although the latter two can often have other purposes as well, as in the Sicilian, for example.