Increment and delay are not the same thing

Both give you a few seconds a move and only one of them lets you finish a move with more time than you started it with. That difference decides how an endgame is played.

+ increment, banks
d delay, does not
Bronstein and simple delay match

Both exist for the same reason. A pure countdown clock means a winning position can be lost because a hand cannot move pieces quickly enough, which decides games on something that is not chess. Increment and delay each hand back a few seconds a move. They hand them back in different ways.

Increment, also called Fischer time

A fixed amount of time is added to your main clock after each move you complete, unless you had already run out. It is written with a plus sign: 3+2, 90+30. Under both the FIDE and the US Chess rules you get the increment for the first move as well as the rest.

The important property is that it accumulates. Any move you play in less than the increment leaves you with more time than you had before it, and that carries forward for the whole game. A player who banks thirty seconds early can spend it on one hard move later.

Delay, in two flavours that behave the same

A delay is a waiting period at the start of each of your moves during which your main clock does not run. Move inside the delay and your clock reads the same as it did before. Take longer and only the excess comes off. It is written with a d: G/90;d5 is ninety minutes for the game with a five second delay.

There are two implementations. Simple delay, sometimes called US delay, holds the main clock still for the delay period and then starts it. Bronstein delay lets the main clock run and then adds back what you used, up to the delay. The time you are left with is identical either way. The difference is what the clock shows you while you think: with a simple delay you can see whether the delay or your own time is counting down, and with a Bronstein delay you read your remaining time without any mental arithmetic.

The one difference that matters

With a delay your main time can only ever go down. The best move you can play is one that costs you nothing. With an increment your time can go up, and over a long endgame it can go up a great deal.

That is why the two are used in different places. Online chess is almost entirely increment, which is why 3+2 and 15+10 are the controls you see. American over the board events have a long tradition of delay, so a tournament pairing sheet may say G/90;d5 where an online lobby would say 90+5. They are not the same control and the arithmetic below is why.

90+5 with an increment, over forty moves, is ninety minutes plus up to 200 seconds of extra clock, and any of it you do not use stays with you.
G/90;d5 with a delay, over the same forty moves, is ninety minutes. The delay stops it going down faster. It never makes it go up.
In a long endgame that gap decides whether a technically won position can be played out at all.

How to read one in the wild

3+2 or 3|2: three minutes, two second increment. The pipe is Chess.com's spelling of the plus.
G/90;inc30: ninety minutes for the whole game, thirty second increment.
G/90;d5: ninety minutes for the whole game, five second delay. A d rather than a plus is the tell.
40/90+30: ninety minutes for the first forty moves, then more time, with a thirty second increment throughout. A slash means the control has more than one stage.

Whichever it is, the second number is folded into the time control category before a game is put in a rating pool, and how it is folded in differs between FIDE and the websites.

No clock at allThe trainer runs without a clock so you can take the time to actually see the position. Speed comes from recognising the pattern, not from hurrying.Open the trainer

Questions people ask

What is the difference between increment and delay in chess?

An increment is added to your clock after each move and accumulates, so moving quickly leaves you with more time than you started with. A delay is a pause before your clock starts running on each move and does not accumulate, so the best you can do is break even. Increment is written 3+2, delay is written G/90;d5.

Can you gain time with a delay?

No. A delay can stop your main time going down on a move, which is the whole point of it, but it can never put time back on. Only an increment can leave you with more time than you had at the start of the move.

Is Bronstein delay the same as simple delay?

In the time you are left with, yes. Simple delay holds your clock still for the delay period and then starts it; Bronstein delay lets it run and then gives back what you spent, up to the delay. Both leave you with the same reading. They differ only in what the clock displays while you are thinking.

Increment and delay sits under The clock in the reference. Nearby: