The Sudoku Times

The goal

Every puzzle is a 9×9 grid of 81 cells. Your job is to fill every empty cell with a digit from 1 to 9 so that no digit repeats within any of the grid's houses — its rows, its columns, and its nine regions. When every cell is filled and no house contains a duplicate, the puzzle is solved.

Some cells are already filled in. These are the givens (or clues): they are part of the puzzle and can never be changed. Everything you deduce must be consistent with them.

The three rules of Classic Sudoku

Rows — each of the 9 horizontal rows must contain every digit from 1 to 9 exactly once. If a row already holds a 7, no other cell in that row can be a 7.
Columns — each of the 9 vertical columns must likewise contain every digit from 1 to 9 exactly once.
Boxes — the grid is divided by the heavy lines into nine 3×3 boxes. Each box must also contain every digit from 1 to 9 exactly once.

Every cell sits in exactly one row, one column, and one box, so each placement you make constrains up to 20 other cells at once. That overlap is the whole game: a digit is correct precisely when it is the only digit that cell can legally hold, or the only cell in a house that can legally hold that digit.

No arithmetic is involved — the digits are just nine distinct symbols. The puzzle would work equally well with nine letters or nine colours.

Jigsaw Sudoku: same game, wilder shapes

In the daily Jigsaw puzzle, the row and column rules are unchanged, but the nine 3×3 boxes are replaced by nine irregular regions — connected clusters of nine cells that interlock like jigsaw pieces. The heavy borders on the board show you where each region begins and ends.

Each region, whatever its shape, must contain 1–9 exactly once.
The shapes change the geometry of your deductions: a region can span four rows, or sit almost entirely inside one column, so a single given can rule out cells in places a 3×3 box never would.
The region layout is part of the daily puzzle — each day's shapes are different, and the same layout is shared by that day's Easy, Medium, and Hard jigsaw puzzles.

Killer Sudoku: arithmetic joins the game

The daily Killer puzzle keeps every classic rule — rows, columns, and the 3×3 boxes — but starts with an empty grid. Instead of given digits, the board is carved into cages: dashed outlines, each with a small number in its corner.

The digits in a cage must add up to the number in its corner.
No digit repeats inside a cage, even where the cage crosses a box boundary.
The cage sums are the only clues — and they are enough: every killer puzzle here still has exactly one solution.

The way in is the extreme sums: a two-cell cage totalling 3 can only be 1+2, a 17 can only be 8+9, and a whole row's cages must together sum to 45. Harder days use bigger cages, whose sums pin down less on their own.

What you're promised

Exactly one solution. Every puzzle published here is checked to have a unique answer, so you never need to guess — there is always a chain of pure logic from the givens to the full grid.
Difficulty is about the road, not the destination. Easy, Medium, and Hard differ in how many givens you start with and how involved the deductions get — the rules themselves never change.
One puzzle per day, per type and difficulty. Everyone solving today's Classic Hard is solving the same grid, and every past puzzle stays available in the archive.

Printable handbooks

Each puzzle type has an illustrated solving handbook — the full technique course as a printable PDF, with worked examples drawn from real archive puzzles: Classic · Jigsaw · Killer.

Tools of the trade

On the board, click a cell (or move with the arrow keys) and type a digit to place it. Conflicts — a duplicate in a row, column, or region — are highlighted as you play, and the Check button audits your progress at any time.

When a cell could still be several things, flip on Notes (or press N) to pencil small candidate digits into the cell instead of committing an answer. Keeping honest candidates is the foundation of nearly every solving technique — the interactive lessons all start from there.