Solve a fresh 9x9 logic puzzle at your level with helpful notes, hints, and accessible controls.
Last updated July 21, 2026
Sudoku is a number-placement puzzle played on a 9 by 9 grid. The grid is divided into nine rows, nine columns, and nine smaller 3 by 3 boxes. Your job is to fill every empty square so that each row, each column, and each box contains the digits 1 through 9 exactly once. The numbers are symbols rather than quantities: you never need to add, subtract, or do any other arithmetic.
Every puzzle begins with some digits already in place. These starting digits are called givens and cannot be changed. They provide enough information to determine the rest of the grid. A good solve comes from comparing the three groups that meet at each square. If a row already contains 1, 2, 3, 5, 6, 7, 8, and 9, its empty square must be 4. More advanced deductions follow the same principle across several squares at once.
Choose Easy, Medium, Hard, or Expert and solve at your own pace. Pencil notes let you record possible digits without committing to an answer, while the Candidates control can fill the currently legal possibilities for you. Hints are available when you want a nudge. The board works with a mouse, touch screen, or keyboard, saves your progress in this browser, and requires no account or download.
The basic rules never change between difficulties. Learn how rows, columns, boxes, entries, and notes work, then use the controls that feel most comfortable.
The fastest opening move is often a simple missing digit. Scan a row and name the numbers it lacks. If only one square is empty, the answer is immediate. Do the same for every column and box. A nearly complete group is easy to overlook when your attention is fixed on one corner, so move through the board in a deliberate order and repeat the scan after every useful entry.
A group with several gaps can still contain an easy answer. Suppose a row is missing 2 and 7. If one empty square's column already contains 7, that square must be 2, leaving 7 for the other position. This is a naked single: only one candidate survives at a particular square. Check all three groups touching the square before you enter it.
Sometimes a square has several possible candidates, yet one of those digits has nowhere else to go in its row, column, or box. That digit is a hidden single. For example, four empty squares in a box may have overlapping notes, but if only one of them includes 6, the 6 is fixed there even though that square also lists other possibilities.
Search for hidden singles by choosing one missing digit at a time. In a 3 by 3 box, trace that digit across the neighboring rows and down the neighboring columns. Existing copies block squares until only one location remains. This crosshatching method is especially effective early in Easy and Medium puzzles and often exposes another single immediately afterward.
Notes are most helpful when they are complete enough to compare. For an empty square, remove every digit already present in its row, column, and box. The remaining digits are candidates. You do not need to fill every note at the very start, but adding candidates to a crowded region can turn a vague problem into a set of small choices.
Keep notes current. When you place a 5, remove 5 from every other empty square in the same row, column, and box. A note reduced to one digit becomes a naked single. If stale notes remain, you may miss that single or mistake an impossible digit for a valid option. The Candidates control can perform the basic legal-candidate scan, while the logical comparison is still yours.
If exactly two squares in one row, column, or box contain the same two candidates, those digits must occupy those two squares in some order. No other square in that group can use either digit. This naked pair may not tell you which member receives which value, but removing the pair's digits elsewhere can reveal a single or another constrained set.
The same idea extends to three squares sharing only three candidates. A naked triple might appear as 1/4, 1/7, and 4/7 rather than three identical note lists. What matters is that the union contains three digits locked into three squares. Make these eliminations only within the group where the set is proven; a pair in one box does not automatically remove those digits from an entire unrelated row.
A hidden pair is the reverse view of a naked pair. If two digits can appear only in the same two squares of a group, those squares must contain that pair even when their note lists include other numbers. Remove the other candidates from those two squares. The board becomes easier to read, and the removed candidates may have been hiding a single.
Hidden pairs are easier to find by scanning digit locations rather than scanning individual squares. Ask where 3 can go in a row, then where 8 can go. If both are limited to the same two positions, you have the pair. This technique becomes valuable on Hard and Expert puzzles, where a large collection of notes may make the simpler relationship hard to see.
When every candidate for a digit inside one 3 by 3 box lies on the same row, that digit cannot appear elsewhere on that row outside the box. The same applies to a column. This is often called a pointing pair or pointing triple. The exact square inside the box may remain unknown, but the shared line still produces useful eliminations beyond it.
You can reason in the other direction as well. If every possible location for a digit in one row falls inside the same box, remove that digit from the box's other rows. This is sometimes called claiming or box-line reduction. Both methods come from the same fact: each digit occurs once in the box and once in the line, so a locked intersection controls both groups.
An X-Wing involves one candidate appearing in exactly two matching columns across two different rows. Whichever of the two positions holds the digit in the first row forces the opposite position in the second. As a result, the digit can be removed from every other square in those two columns. The pattern can also be rotated, using two columns and two matching rows.
Do not search for X-Wings before checking singles, pairs, and box-line interactions. Advanced patterns are slower to inspect and are easy to imagine where their requirements are not exact. First make sure the candidate occurs only in the two corners on each base row or column. Then limit eliminations to the two cover lines; the other candidates in the base lines are part of the pattern and must stay.
When no answer looks immediate, choose a highly constrained square and follow each candidate's consequences in your head or with careful notes. If placing one candidate would force a duplicate or leave a digit with no location in a group, that candidate is impossible. This contradiction method can reveal a valid elimination without permanently entering an uncertain value.
Before starting a long chain, rescan the entire grid. Solvers often feel stuck because they have not revisited a box changed by the last entry. Check for naked singles, hidden singles, locked candidates, and pairs in that order. If you still choose to test a possibility, keep the branch clearly separated from proven work and use Restart if you want to return to the original puzzle state.
A steady rhythm reduces missed clues. Scan boxes for missing digits, then rows, then columns. Fill proven singles, update notes, and repeat. When singles run out, inspect constrained groups for pairs and locked candidates. Every elimination changes the puzzle, so return to the simple scan before looking for another advanced pattern. The easiest deduction available is usually the safest one to make next.
Use highlighting and focus as orientation tools, not as substitutes for checking the rules. Selecting a digit can help you count its eight completed copies and find the region that is still missing it. On a phone, work one box at a time while also checking the full row and column. On a keyboard, arrows keep your place while the number keys let you enter a confirmed value without moving to the number pad.
Easy puzzles are ideal for learning complete scans and noticing singles without rushing. Medium puzzles reward accurate candidate notes and box-line interactions. Hard puzzles are more likely to require pairs, triples, or deductions that connect distant regions. Expert puzzles can keep many candidates alive until one precise elimination unlocks a long sequence of placements.
Difficulty is not a measure of intelligence, and a faster time is not the only sign of progress. Aim first for correct, explainable moves. Use a hint to learn when a technique is unfamiliar, replay with Restart to inspect a difficult position again, or press G for a different puzzle when you want a fresh pattern. Consistent reasoning becomes speed naturally as common relationships grow familiar.
Yes. You can play Sudoku here for free in your browser with no download, account, or signup. Easy, Medium, Hard, and Expert puzzles are included.
Fill the 9 by 9 grid so every row, every column, and every 3 by 3 box contains the digits 1 through 9 exactly once. The starting givens cannot be changed.
No. Sudoku uses digits as nine distinct symbols. You solve by finding which symbol can legally fit each square, not by adding, multiplying, or calculating totals.
A row runs horizontally, a column runs vertically, and a box is one of the nine outlined 3 by 3 regions. Every square belongs to exactly one of each, and its digit must work in all three.
Pencil notes are small candidate digits recorded inside an empty square. They help you remember which values remain possible. Notes are planning marks, not final answers, and you can toggle them at any time.
Candidates fills notes with digits that are not currently present in each square's row, column, or box. It organizes legal possibilities but does not identify the final answer among them.
A properly formed standard Sudoku puzzle has a unique solution. The puzzles in this game are generated and checked so that the givens lead to one completed grid.
Easy emphasizes direct singles, while Medium, Hard, and Expert require progressively longer or less obvious deductions. Difficulty depends on the solving path as well as the number of givens, so clue count alone does not define a level.
Yes. Arrows move between squares; 1-9 enters a digit; Backspace, Delete, or 0 erases; N toggles notes; H gives a hint; C fills candidates; R restarts; G begins a new puzzle; M mutes sound; and S opens settings.
Yes. Your active puzzle and progress are saved in this browser so you can leave the page and continue later. Browser storage is local to the device and browser profile you are using.