Sudoku Vault is a free online sudoku puzzle game that challenges your logic skills across three grid sizes — 4x4, 6x6, and 9x9 — each available in Basic, Normal, Hard, and Expert difficulty. Whether you're just learning how sudoku works or grinding through Expert-level 9x9 grids, every puzzle is a clean, satisfying test of deductive reasoning.

The built-in NOTES feature lets you pencil in candidate numbers across cells, so you can track possibilities without losing your place — a must-have tool for harder puzzles. The CHECK button is a smart progress tool: it wipes out any wrong entries and permanently locks your correct ones, keeping the board clean and your focus sharp. The interface is minimal and distraction-free, which means you spend time actually solving, not fumbling through menus.

Sudoku Vault is a great pick for anyone who enjoys free brain training games, logic puzzles for adults, or educational number games for kids learning math patterns. It covers everything from easy sudoku for beginners to hard sudoku puzzles that will genuinely test experienced players. If you're searching for a free sudoku game with multiple grid sizes, no download required, playable directly in your browser — this is exactly that. Bookmark it for your daily mental workout.