How to Play Sudoku Online: Rules, Controls, and Your First Puzzle
Sudoku is a logic puzzle played on a 9×9 grid. To solve it, you fill every empty cell with a digit from 1 to 9 so that no digit repeats in any row, any column, or any of the nine 3×3 boxes. On a site like Sudoku Place, you can start a puzzle in the browser, type numbers into cells, and use controls such as Restart, Check, and New Puzzle. This guide covers the rules, the typical on-screen controls, and a simple method for working through your first grid.
The Rules in Plain Terms
A standard Sudoku grid has three overlapping constraints:
- Rows: Each of the 9 horizontal rows must contain the digits 1–9 exactly once.
- Columns: Each of the 9 vertical columns must contain the digits 1–9 exactly once.
- Boxes: Each 3×3 box (there are nine of them) must contain the digits 1–9 exactly once.
A puzzle starts with some cells already filled in. These are called givens, and they are fixed — you don't change them. Your job is to fill the remaining cells so all three constraints hold. A well-formed puzzle has exactly one solution, reachable by logic alone; you never need to guess.
What the On-Screen Controls Do
Online Sudoku adds a few conveniences that paper can't match. The exact layout varies by site, but the Sudoku Place page shows controls including Restart, Check, and New Puzzle. Here's what those typically mean and how to use them:
| Control | What it does | When to use it |
|---|---|---|
| Click a cell | Selects it so you can type a number | To enter or change a digit |
| Number keys / keypad | Places the chosen digit in the selected cell | Filling in an answer |
| Erase / Delete | Clears a digit you entered | After a mistake or a change of mind |
| Restart | Clears your entries and returns to the original givens | When you want a clean attempt |
| Check | Flags cells that conflict with the rules | To find an error without starting over |
| New Puzzle | Loads a fresh grid | When you finish or want a different puzzle |
The key difference from paper: the game can tell you immediately when a digit breaks a rule. On paper you'd have to scan the row, column, and box yourself. Online, a conflicting entry is often highlighted, which makes early mistakes much easier to catch.
Solving Your First Puzzle Step by Step
Work through the grid using the constraints, one cell at a time. Here's a reliable beginner routine:
- Scan for the easiest cells. Pick a digit, say 1, and look at each 3×3 box. If a box already contains a 1, skip it. If it doesn't, check whether the rows and columns crossing that box already have a 1 — if eight of the nine cells are ruled out, the last one must be the 1.
- Use "only one place" logic. Within a single row, column, or box, ask: for this digit, is there only one empty cell it can legally go in? If so, place it.
- Use "only one number" logic. For a single empty cell, ask: which digits are still allowed here, given its row, column, and box? If only one digit fits, that's the answer.
- Repeat. Every digit you place removes options from its row, column, and box, which often unlocks the next cell. Loop steps 1–3 until the grid is full.
Using Notes (Candidate Numbers)
When a cell has two or more possible digits, many players write small "candidate" numbers in it — the digits that aren't yet ruled out. This is the online equivalent of pencil marks on paper. Filling in candidates for a tricky region lets you spot patterns like a digit that appears as a candidate in only one cell of a row.
Start without notes if the puzzle is easy; add them when you get stuck.
When You Get Stuck
Getting stuck usually means one of two things: you've made an error, or you've hit a spot that needs a slightly deeper technique. Try these in order:
- Check for conflicts. Run the Check control, or manually verify that no digit repeats in any row, column, or box. A single wrong entry can block progress across the whole grid.
- Undo or erase recent entries. If you're unsure where the mistake is, back out your last few placements and re-derive them.
- Restart if needed. Restart returns you to the original givens, which is faster than hunting for one bad cell in a nearly full grid.
- Re-scan with fresh eyes. Pick a digit you haven't focused on and sweep the whole board for it.
If the puzzle is genuinely hard rather than broken, the next step up from single-candidate logic is looking for pairs and other patterns — but for a first puzzle, the two techniques above are usually enough.
Online vs. Paper Sudoku
The puzzle itself is identical; the experience differs in a few practical ways:
- Instant feedback: Online grids can highlight rule violations as you type. Paper gives none.
- Timing and hints: Many online versions track your time and offer hints. Paper relies on you.
- Daily puzzles: Sites often publish a new puzzle each day, so there's always a fresh grid without buying a book.
- No erasing: You can change any entry freely, which makes experimenting less costly than on paper.
If you want to try it right now, open the Sudoku Place page, click New Puzzle if you want a different grid, select a cell, and start with the easiest digit to place. Use Check whenever you're unsure, and Restart if you'd rather begin clean.