sudoku tutorial
this guide teaches sudoku step by step for beginners and advanced players. start from the easy logic first, then grow into pattern-based techniques as puzzles become harder.
how it works
sudoku is solved by logic, not guessing. each move follows the same core rule and candidate elimination.
- every row must contain digits 1 through 9 exactly once.
- every column must contain digits 1 through 9 exactly once.
- every 3×3 house must contain digits 1 through 9 exactly once.
- use candidates to eliminate impossible numbers until one valid choice remains.
learn more
click any technique to learn morelevel 1
last free cell
when only one spot is empty, fill it with the missing number.
level 1
last remaining cell
for a chosen number, only one position in a unit can accept it.
level 1
last possible number
use row, column, and box constraints to find the only valid digit.
level 2
obvious single
a cell has exactly one candidate note left, so place it.
level 2
hidden single
a number appears as candidate in only one cell of a unit.
level 3
obvious pairs
two cells share the same two candidates, remove them elsewhere.
level 3
hidden pairs
two numbers are restricted to two cells, trim other notes there.
level 3
pointing pairs
box candidates aligned in one line eliminate candidates outside the box.
level 4
obvious triples
three cells contain only three shared candidates, eliminate from peers.
level 4
hidden triple
three digits are confined to three cells, remove extra notes there.
level 5
x-wing
a rectangle pattern across two rows and columns removes candidates.
level 5
y-wing
pivot and wing pattern forces candidate elimination in shared peers.
level 5
swordfish
advanced three-line pattern that removes candidates across three columns or rows.