Hardest Sudoku

Sudoku puzzles by difficulty

Every puzzle below is graded on the SE grade scale. Open one to see the grid and play it free in your browser.

By The Hardest Sudoku Team · Last updated

TL;DR

500 graded puzzles, organised by SE band — from singles-only warm-ups to monster-grade chains.

SE grade 1 — The gentlest puzzles. Solvable end-to-end by spotting naked and hidden singles — no candidate bookkeeping required.

27 more in this band.

SE grade 2 — Easy puzzles that still resolve through singles, but you may need to scan more carefully before the next placement appears.

57 more in this band.

SE grade 3 — Intermediate. Pairs and locked candidates (pointing/claiming) start to matter — you eliminate candidates rather than place values directly.

92 more in this band.

SE grade 5 — Hard. Basic fish (X-Wing) and consistent candidate elimination across rows and columns become the bread and butter.

92 more in this band.

SE grade 7 — Expert. Wings (XY-Wing) and larger fish (Swordfish) appear; progress often depends on chaining one elimination into the next.

92 more in this band.

SE grade 8 — Diabolical. Simple techniques run dry early; you lean on forcing chains and careful candidate logic to break the puzzle open.

81 more in this band.

SE grade 11 — Monster territory. These puzzles have no easy entry point and demand long forcing chains end to end — the home of AI Escargot, Golden Nugget and Platinum Blonde.

3 more in this band.