Hard Sudoku puzzles

Hard Sudoku is for players who already have the basics down. Grids start with far fewer given digits, so scanning alone won't carry you through — you'll lean on candidate notes and pair/triple elimination to narrow things down.

Hard puzzles reward patience: working through candidates systematically, one unit at a time, rather than hunting for the next obvious placement.

Techniques for Hard Sudoku

Every puzzle here is generated to require specific solving techniques, not just picked at random — this is what hard actually means on Ranked Sudoku:

From practice to ranked play

Most Sudoku sites end at the puzzle. Ranked Sudoku doesn't: a solve you finish here — even before signing up — can become an opponent for someone else to race. Create a free account and you can race real players' recorded solves yourself, beat their time, and climb an ELO rating that tracks how you're actually improving, not just a streak counter.