How to Play Bulls and Cows

The rules, a worked example, and a simple strategy that cracks any code — plus a free daily version you can play right now.

▶ Play today's free Bulls & Cows puzzle — Vaultle

What is Bulls and Cows?

Bulls and Cows is a classic code-breaking game for the mind — older than its famous commercial cousin Mastermind. One player thinks of a secret number whose digits are all different (4 digits is the most common version), and the other player tries to crack it with as few guesses as possible.

The rules

• The secret code has 4 different digits (0–9, no repeats).
• You guess a 4-digit number with no repeated digits.
• Each guess is scored with two clues:
  • Bull — a correct digit in the correct position.
  • Cow — a correct digit in the wrong position.
• You're told only the counts of bulls and cows — not which digit is which. That's the whole challenge.
• Crack the code when you score 4 bulls.

A worked example

Say the secret code is 1 9 0 5:

Your guess	Bulls	Cows	Why
0 1 2 3	0	2	0 and 1 are in the code but misplaced
1 0 4 5	2	1	1 and 5 are placed right; 0 is in the code but misplaced
1 9 0 5	4	0	cracked!

Strategy: how to crack it every time

Bulls and Cows is pure deduction — no luck required. Here's a reliable approach:

1. Open with four distinct digits (for example 0 1 2 3). The total of bulls + cows tells you how many of those four digits appear in the code.
2. Test fresh digits early. In your next guesses, swap in digits you haven't tried yet so you quickly learn which of the ten digits are in the code.
3. Turn cows into bulls. Once you know a digit is in the code (a cow), move it to different positions on later guesses until it becomes a bull.
4. Only guess codes that fit every clue so far. If a candidate code would have produced different bull/cow counts on a past guess, eliminate it. Keep doing this and you converge fast.

With this method almost every code falls in five or six guesses, and even the trickiest distinct-digit code is always solvable within nine.

Play Bulls and Cows online (free, daily)

Want to practice? Vaultle is a free daily Bulls & Cows game: everyone gets the same secret code each day, you crack it in nine guesses, and you can share your spoiler-free result grid. No login, no ads, works on mobile — and there's an unlimited practice mode for when you want to keep going.

▶ Crack today's code on Vaultle

FAQ

Is Bulls and Cows the same as Mastermind? They're the same idea. Mastermind is the colored-peg board-game version; Bulls and Cows is the original played with digits.

Can the code have repeated digits? The classic version uses all different digits, which keeps the deduction clean. That's the version Vaultle uses.

How many guesses should it take? A careful player usually needs five or six; nine is plenty of headroom.