Sudoku checker and solver!

Choose your level of sudoku from the buttons below, or enter numbers from a sudoku you want to solve. You can then either:

Choose a sudoku to solve

Check your solution, or have the browser solve the sudoku:

[Note that this algorithm will attempt to solve the sudoku even if this takes a very long time, and your browser will be occupied during this process. A backtracking algorithm is used. This means values are tried from top left to bottom right, working along rows, checking that each value is valid. If an impasse is reached, the algorithm will take a step backwards.]