How the solvers work
Every solver uses a fixed, published method: search algorithms for the cubes (Herbert Kociemba's two-phase algorithm for the 3x3), constraint search for sudoku and the other grid puzzles, and game-tree search for board games. The work happens in your browser, usually in a background worker so the page never freezes. Nothing you enter is sent to a server, and the camera scan of the Rubik's cube solver reads the video on your device without recording it.
How each solver is tested
The rule for every page is that it must never give a wrong answer. Each engine has its own automated test that solves many random or known puzzles and checks every answer independently: cube solutions are replayed on a separate cube model, grids are checked against the rules, and game moves are compared with a separate brute-force search. Impossible input (two identical cube pieces, a row with two 7s) must be detected and explained. A few of the results:
- 3x3 cube: 500 of 500 random cubes solved in the first trial run, no solution longer than 22 moves; the full test solves 2,000 random cubes and replays every solution. With the two-second search for a shorter solution, 279 of 300 random cubes (93%) came out at 20 moves or fewer.
- 4x4 cube: 300 of 300 random states solved and replayed, 70.4 moves on average.
- Skewb and pyraminx: 25,000 positions each, solved and replayed; 400 of 400 checked as the shortest possible solution (for the pyraminx, not counting the tips).
- Sudoku: 2,858 checks and 30,707 hint steps compared with the true solution, with no wrong placement or removal.
- Connect 4: 250 late-game positions compared column by column with an independent brute-force search.
- Minesweeper: mine odds on 266 small boards compared with a brute-force count of every layout.
- Mastermind: all 1,296 codes of the classic game cracked in at most 5 guesses.
- Nonograms: the line solver compared with brute force on 4,000 random lines.
- Cube algorithms: all 299 algorithms on the algorithm pages replayed on a cube model; 18 drafted algorithms that failed the replay (they solved a different case or broke solved pieces) were corrected or removed before launch.
Each solver page ends with the date its solver was last tested. Pages that explain rules also list their sources.
Solvers only
We solve what you enter. We do not publish answers to any newspaper, app or daily puzzle.
Open-source code
The 3x3 cube solver and the 3x3 stage of the 4x4 solver use cubejs (MIT license), an implementation of Herbert Kociemba's two-phase algorithm. The chess move calculator runs Stockfish.js 19 (lite, single-threaded), unmodified, in its own worker; Stockfish is free software under the GNU General Public License version 3 (license text, source code, also on GitHub). Chess move rules use chess.js (BSD 2-Clause license). All other solvers are our own code.
Trademarks
Rubik's Cube is a trademark of Spin Master. Connect 4 is a trademark of Hasbro. This site is not affiliated with or endorsed by either; the names are used only to describe which puzzle a solver solves.
Contact and corrections
If a solver gives a wrong answer, or rejects a puzzle that is valid, tell us which page it was and what you entered. The quickest way is the share link from the bar under the tool, which carries your puzzle. We fix the solver, re-run its test and update the tested date on the page.
Email: hello@puzzletip.com.