Stockfish says mistake ?

Hello guys,

I have a question about stockfish, i can't understand why my move 20: g6 is considered as a mistake ?

My game : http://fr.lichess.org/3v1t12Xp

If someone has an explaination ? ;)

Thanks !

Well.

There is a hanging bishop which you didn't take. You went for a fork, which is not as good, and also the computer line shows that black can escape that fork threatening mate on g2 after Qe4.

So, to sum it up, instead of taking a free piece you went for a fork that wasn't really a fork :P

Cheers!