Sudoku: give every digit a reason

Know what a placement must satisfy

In a standard Sudoku, each row, column and three-by-three box uses the digits one to nine without repeating them. A placement must satisfy all three views at once. Sudoku.com offers difficulty choices and tools such as notes and hints; inspect the current settings before starting.

Separate a candidate from an answer

A digit that could fit is a candidate. It becomes an answer only when you can rule out the alternatives relevant to that cell or locate the digit uniquely in a group. Keep those two states distinct so a tentative idea does not quietly become a fact.

Start in a part of the grid with enough information to compare. After one justified placement, scan its row, column and box again. A small change can make another relationship easier to see.

A routine for the first puzzle

• Choose a difficulty that leaves room to learn.
• Read the rules and decide which help settings you want.
• Find a cell or group where several possibilities are already excluded.
• Explain a placement in a sentence before entering it.
• If you use a hint, understand its reasoning before making the next move.

Pause without rushing the answer

When you get stuck, a brief pause can be more useful than an unsupported guess. Note the part of the grid you were analysing and return when you want to. The website advertises free play supported by ads; an offer or another puzzle does not need to extend your session.

Before you open the publisher.

Free browser puzzles with advertising. Difficulty and help features are available; review the site's current settings.

Current public puzzle page, rules and advertising disclosure reviewed; no hands-on rating.

Publisher source