Enter the recorded attempts

Choose the code rules, then enter each guess and its exact / misplaced feedback. The page also shows peg-style feedback previews so it feels more like Mastermind. Leading zeroes count.

Solution

The solver tests every allowed code against every reported attempt.

Create a unique puzzle

Pick your rules, and the generator will create attempts that leave exactly one possible code. The hidden answer is never included in the shared puzzle text or URL.

The challenge is generated on your device. No account, API, or database is needed. A few harder combinations may require more clues.

Only reveal or copy the answer when you want to check your puzzle. Printing and sharing leave it out.

Puzzle preview

This is what you can put into your geocache listing.

Play Mastermind Codebreaker

Crack a secret random code. Each guess gives you exact and misplaced pegs. Green means the right digit in the right spot; gold means a right digit in the wrong spot.

Select a position on the board, then tap a number below it. When all positions are filled, press Submit Guess.

Tap a position on the board, then choose its number. All previous guesses stay visible.

Mastermind board

Your guesses appear here with colored feedback pegs. Feedback indicates counts, not which individual digits match.