Your own pawns decide which bishop is which

A bishop is not good or bad because of where it stands. It is good or bad because of the colour of the squares your own fixed pawns are sitting on.

Test count your fixed pawns on the bishop's colour
Classic case the c8 bishop in the French Defence
Counterpoint bad bishops protect good pawns

The test takes five seconds. Look at your pawns, ignore the ones that can still move freely, and count how many of the fixed ones are on light squares and how many on dark. Your bishop on that colour is the bad one. It is bad in the exact sense that its own army is standing on the squares it wants to use.

This matters more than it sounds, because pawns are the pieces least able to change their minds. A knight that is badly placed today is well placed in three moves. A bishop stuck behind a fixed pawn chain is stuck for as long as the chain lasts, which is often the rest of the game.

The French Defence bishop, in one number

An Advance French. Black's light-squared bishop on c8 has exactly one legal move, and it is d7, where it is still behind the pawns.

One move later. White's light-squared bishop, the same colour, the same stage of the game, has five.

Nothing separates those two bishops except pawns. Black's pawns on d5, e6 and f7 are all light squares, so the light-squared bishop has nowhere to look. White's pawns on d4 and e5 are dark, so White's light-squared bishop has the whole board.

Be honest about the other half of it, though. White's dark-squared bishop is also standing behind pawns on its own colour, and strong players will argue for an hour about how much that costs. The difference is space: White's restricted bishop is behind a chain that is two ranks further up the board, so it has room to manoeuvre behind it and Black's does not.

Three ways to fix a bad bishop

Trade it. This is the main plan and it is why Black plays ...b6 and ...Ba6 in half the French lines, or ...Bd7 and ...Bb5. A bad bishop swapped for a good one is a whole positional advantage undone in one move.

Or move the pawns off its colour. In the French that means ...f6, hitting the chain at its base, which is the second main plan and the reason the whole opening is playable. Or get the bishop outside the chain before you commit the pawns, which is the entire point of the Caro-Kann: 1.e4 c6 2.d4 d5 3.Nc3 dxe4 4.Nxe4 Bf5 develops that same bishop to a good square before ...e6 shuts it in.

There is a real counter-argument, and it is worth knowing. A bad bishop is frequently the piece holding your position together, because the pawns it is stuck behind are the pawns it is defending. Trade it off at the wrong moment and you do not get a good bishop, you get a collapsing pawn chain and a set of weak squares. Bad bishops protect good pawns.

Only fixed pawns count. Pawns that can still advance are not part of the judgement.
A bad bishop outside its own chain is not bad at all, which is why getting it out early is worth a tempo.
In an endgame with pawns on both wings, a good bishop usually beats a knight and a bad bishop usually loses to one.
If you cannot trade or free your bad bishop, aim to trade the other three pieces instead and reach an endgame where it defends rather than attacks.

Questions people ask

What is a bad bishop in chess?

A bishop whose own pawns are fixed on the colour of squares it travels on, so it has few squares and cannot easily reach the other side of its own structure. The classic example is Black's light-squared bishop in the French Defence, sitting on c8 behind pawns on d5, e6 and f7. Nothing is wrong with the bishop; the pawns are what make it bad.

Is a bad bishop worse than a knight?

Often, yes, and that is the usual practical decision. A knight does not care what colour the squares are, so in a locked position with pawns fixed on one colour, the side with the knight is generally happier. In open positions with pawns on both wings, even a mediocre bishop tends to outrun a knight, so it depends on whether the structure can still change.

How do I get rid of a bad bishop?

Trade it, free it, or reroute it outside the pawn chain, in that order of ease. Trading usually means manoeuvring it to a diagonal where your opponent's good bishop has to meet it. Freeing it means a pawn break that unfixes the structure. Rerouting means moving it round the outside, which costs time but often works in a closed position where you have time to spend.

Good and bad bishops sits under Pieces and squares in the reference. Nearby: