About Sudoku365

Who This Site Is For

Sudoku365 is a free Sudoku site for people who want a steady supply of well-made puzzles, clear explanations of the techniques that solve them, and a lightweight experience that loads quickly on any device. Whether you play one puzzle a day on a coffee break, grind through expert-level grids on the weekend, or use Sudoku to introduce logical thinking to younger readers, the site is designed to stay out of your way.

The audience ranges from complete beginners — people who have never filled in a 9×9 grid — to experienced solvers looking for harder challenges and patterns like X-Wing and Swordfish. The same archive serves both groups, because each day publishes four puzzles at different difficulty levels.

What We Cover

The site has three content pillars:

• Daily puzzles. A full calendar of classic 9×9 Sudoku puzzles for 2026, with Easy, Medium, Hard, and Expert versions for every date. Puzzles are permanently archived, so you can go back and play any date you missed.
• Strategy tutorials. Step-by-step explanations of the common Sudoku techniques — naked singles, hidden singles, scanning, naked and hidden pairs, locked candidates, X-Wing, Swordfish, Y-Wing — written for readers who want to understand why a technique works, not just memorise its name.
• Variants and background reading. An educational overview of Sudoku variants (Killer, Samurai, Mini, 6×6, Hexadoku, Sudoku X, Jigsaw, Hyper) and a short history of how the puzzle reached its current form.

Editorial Approach

The goal is accuracy first and readability second. Strategy articles are written so that a reader can follow along with a real puzzle in front of them. Rules are stated plainly, examples use concrete positions rather than abstract references, and the explanations favour the shortest correct path through each technique.

Content is reviewed when generation tooling changes, when Sudoku solving conventions shift (they rarely do, but terminology varies), or when reader feedback points out a gap. Each substantive page shows a "Last reviewed on" date so you can see how fresh the material is.

No fake experts, fabricated testimonials, or invented statistics appear anywhere on the site. General statements use plain phrasing ("many solvers", "general practice", "commonly used in Medium puzzles") rather than numbers that would need a source.

How Puzzles Are Produced

Each puzzle is generated programmatically. The generator starts from a fully completed 9×9 solution grid that satisfies all three Sudoku rules, then removes clues one at a time while checking that the remaining puzzle still has exactly one unique solution. The removal strategy is tuned so that the resulting puzzle requires techniques appropriate to its stated difficulty.

Every puzzle is verified to have a single unique solution reachable using logic — no puzzle requires guessing. If a grid slipped through with ambiguity, it would be a bug, and we ask readers to report any suspected cases through the Contact page.

Technology and Performance

Sudoku365 is a static site. Every puzzle page, every strategy article, and every index is pre-rendered to plain HTML before it reaches your browser. There is no framework, no build step in the browser, no loading spinner. The only JavaScript on a puzzle page is a small, dependency-free game engine that handles input, timing, and pencil marks.

The benefits of this approach are practical: fast loading on slow connections, no layout shift, and pages that can be printed straight from the browser. The SVG logo and icon sprite scale cleanly on any display, and the CSS uses Grid so the puzzle board lays out identically across screen sizes.

Privacy and Advertising

The site uses Google Analytics to understand aggregate site traffic, and uses or intends to use Google AdSense to display advertising that supports free access to the content. No accounts, email addresses, or personal profiles are collected by the site itself — we do not run a login system. The Privacy Policy covers what third-party services record, and the Cookie Policy lists the cookie categories in use along with opt-out links.

Game progress (the digits you enter, the theme you chose, whether you had a puzzle open) is stored in your browser using Local Storage. That data stays on your device and is never transmitted to our servers.

Short History of Sudoku

The modern form of Sudoku is usually traced to the late 1970s, when a puzzle called "Number Place" appeared in American puzzle magazines. A Japanese puzzle publisher later popularised the format under the name Sudoku, a contraction of a phrase meaning roughly "the digits must occur only once". The puzzle reached a wide international audience in the mid-2000s, when newspapers in the United Kingdom and elsewhere began printing daily grids.

Today Sudoku appears in newspapers, magazines, puzzle books, mobile apps, and websites around the world. The rules are unchanged from the version that captured attention two decades ago: fill a 9×9 grid with digits 1 to 9 so that every row, column, and 3×3 box contains each digit exactly once.

Why Sudoku?

Sudoku sits in a useful spot between casual entertainment and mental exercise. A puzzle is short enough to play on a commute but deep enough to reward study. The rules are language-independent, which makes the game accessible across reading levels and cultures, and the feedback is immediate — a wrong entry blocks a later deduction, so mistakes surface quickly.

Regular solving is associated with general benefits of doing any focused, logic-oriented activity: sustained attention, working memory practice, and the satisfaction of finishing a well-defined task.

Contact

Feedback, corrections, and suggestions are welcome. The Contact page lists the email address and describes what to include in bug reports, puzzle-error reports, and feature suggestions. We read every message.