How to win at Codebreaker

A hidden code, and after each guess two numbers: how many are exactly right, and how many are right but misplaced.

You guess a sequence of colours. The feedback is two counts — exact matches in the right position, and correct colours in the wrong position. Everything depends on reading the second number correctly.

What "right colour, wrong place" really counts

This is where people go wrong. The two counts are computed against multisets: exact matches are removed first, then the remaining colours are matched up as far as they can be. A colour appearing twice in your guess but once in the code contributes at most one.

So a total of 4 across both numbers with a 4-long code means you have exactly the right colours in some order — a very strong position, and easy to miss if you only read the first number.

Opening well

Do not open with four of the same colour. It is a wasted turn: it tells you only how many of that colour appear.

Open with two pairs — say red, red, blue, blue. This gives information about two colours at once and, crucially, the split between exact and misplaced tells you something about position as well as content.

Every guess should eliminate

The habit worth building is to make guesses that are consistent with everything you already know. If previous feedback rules out a code, do not guess it: you learn nothing you could not have deduced. A guess consistent with all prior feedback is guaranteed to teach you something, because it either is the code or is eliminated.

Changing one position at a time is intuitive but slow. Changing two and reading how the counts move carries more information per turn.

The deduction mode

The deduction puzzles give you a set of guesses with their feedback and ask you to work out the code. Every row in them is load-bearing: the generator removes any row that could be deleted while leaving the answer unique. So if you cannot finish, you have not yet used every row — there is no filler.

Frequently asked questions

How is the misplaced count worked out?

Exact matches are found and removed first, then the remaining colours in your guess are matched against the remaining colours in the code. A colour you guessed twice that appears once in the code counts once.

What is a good first guess?

Two pairs, such as two of one colour and two of another. It reveals information about two colours and about position simultaneously, unlike four of a kind which reveals almost nothing.

Are the deduction puzzles always solvable?

Yes, and every clue row is necessary — the generator removes any row that is not, so nothing shown is padding.