Best Free Sudoku Apps and Websites (2026)

The best free sudoku app is the one whose pencil marks, hints and error checking match how you actually solve, and that is a different answer for a beginner than for someone working through expert grids. There is no single winner, and any list that names one is really telling you about the writer's habits rather than yours.

One thing up front. This article deliberately does not quote prices, star ratings, download counts, subscription tiers, or feature checklists for named products. Those change constantly, often within weeks of publication, and roundups that lead with them are wrong more often than right. What does not change is the set of things worth checking, so that is what this page covers: the categories that exist, the eleven features that separate a good sudoku experience from a frustrating one, and how to test them in five minutes.

The categories of free sudoku, and what each is good for

Big free browser puzzle portals

These are the general puzzle sites hosting many game types together: sudoku alongside solitaire, mahjong, crosswords, word searches, jigsaws. You play in a browser tab, nothing installs, and it is all paid for by advertising. If you have ever searched "24 7 games sudoku" you have met this category, which is built around breadth.

The strengths are real: no install, no account for basic play, a large catalog. So are the trade-offs. Ad load tends to be the heaviest of any category, difficulty grading is often inconsistent because the puzzles come from different sources, and the interface is usually shared across dozens of games rather than designed for sudoku, which shows most in how pencil marks behave.

Newspaper and syndicated puzzle sites

Most major newspapers run a daily sudoku online. The appeal is a known standard: the same setter or supplier every day, a difficulty that means what it says, and a routine you can build a habit around. The limits are structural. You usually get today's puzzle free and pay for the archive, the difficulty is fixed rather than chosen, and the player is often a licensed widget rather than something the paper built.

Puzzle-supplier sites

Behind a lot of newspaper and book puzzles sit specialist suppliers who generate, test and license grids at scale. Conceptis is the best-known name here, a long-established supplier of logic puzzles including sudoku and the picture-logic puzzles it is particularly associated with, whose grids appear in newspapers and puzzle books worldwide. Searching "conceptis sudoku" turns up both their site and outlets that syndicate them.

What you get here is consistency. Supplier grids are validated, difficulty is graded by a solver that models human techniques rather than by counting givens, and the same rating means the same thing across the catalog. Expect the free selection to be a rotating sample of a bigger paid one.

Lean single-purpose community sites

There is a small, valuable category of sites that do exactly one thing: serve a good grid in a fast, clean page with no account, no ads and no upsell. Sudoku exchange is the kind of site solvers recommend to each other for precisely this reason, a minimal free browser sudoku with a clean interface and none of the surrounding noise.

These sites tend to be built by solvers rather than publishers, which shows in the details that matter to people who solve a lot: sane keyboard input, candidate handling that behaves as experienced solvers expect, and a page that loads instantly. What you give up is bookkeeping: no stats, no streaks, no sync, no tutorials. For many solvers that is the appeal.

Big mobile app-store sudoku apps

The large free sudoku apps on iOS and Android are the most polished solving experiences available, competing mainly on touch input, difficulty range, statistics and daily challenges. Input quality is far ahead of most browser play.

The thing to examine is what "free" means in each one, because it varies enormously between apps that look identical in a store listing. Some are ad-supported with an optional one-off purchase to remove ads, some meter hints, some gate the harder levels. The business-model section below covers how to tell which you have.

Generator and printable sites

This is the category this site sits in. A generator makes puzzles to your specification, at a chosen size and difficulty, and prints them, which is a different job from serving one puzzle at a time on screen.

Generators matter for four groups: teachers who need thirty copies of a graded worksheet, parents starting a child on 4x4 and 6x6 grids, anyone who prefers paper because pencil marks beat any app's notes mode, and solvers who want a variant their app does not offer. If that is you, our sudoku generator makes and prints grids across a range of sizes and difficulty levels. What generators do not do is track stats or teach on screen, so most people who use one keep an app too.

Open-source and no-ads options

Sudoku apps distributed as open source, most easily found through open-source app repositories, share a character: no ads, no accounts, no analytics, no upsell, and no attempt to make solving a habit loop. Interfaces are plainer and tutorial content is rare. If your objection to free sudoku apps is the advertising and data collection rather than the puzzles, start here.

The eleven things worth checking

Test these on any candidate and you will know within a few puzzles whether it suits you.

Pencil marks and candidate notes

This is the single biggest difference between apps. Manual pencil marks mean you write candidates yourself. Auto-candidates mean the app fills every possible digit into every empty cell and updates them as you place digits.

That changes the game, not just the convenience. Maintaining your own candidate list is a large part of the skill, and the mistakes you make maintaining it are where a lot of learning happens. Turn auto-candidates on and techniques like naked pairs become visible rather than found.

What to check: can you turn auto-candidates off entirely? Does the app auto-remove a candidate when you place a conflicting digit, and can that be disabled separately? Is there a fast way to enter several candidates without switching modes each time?

Difficulty grading, and whether it is honest

Honest grading rates a puzzle by the hardest technique required to solve it, not by how many clues it starts with. A 26-clue grid needing an X-Wing is harder than a 24-clue grid that falls to singles.

Test it by solving two or three at a level you know well. If puzzles labeled "hard" fall to basic scanning, the grading is cosmetic and the expert tier will not stretch you either. Apps that name the techniques a puzzle requires are being transparent about grading.

Error checking and undo

Three models exist. Instant check flags a wrong digit the moment you enter it. Check on demand validates only when you ask. No checking tells you nothing until the end.

Instant check is comfortable, and it removes a real part of the puzzle: knowing a digit is right the moment you place it means you never verify your own reasoning. If you want to improve, check on demand is better, since errors stay findable without becoming free. Look for an app that lets you choose. Deep undo matters too, because backing out of a wrong branch without restarting is what makes hard puzzles playable on screen at all.

Hint quality

A hint that names the technique is worth ten hints that fill a cell. "R4C7 is 6" teaches nothing. "There is a hidden single for 6 in box 5" teaches you where to look next time.

This is the clearest quality signal in the category, and it is easy to test: get stuck deliberately, ask for a hint, read what it says. Apps that only fill cells are serving puzzles; apps that name techniques are teaching.

Offline play

Check by turning on airplane mode and opening the app. Some generate puzzles on the device and work indefinitely offline, some cache a handful, some fetch every puzzle from a server and show you a spinner on the subway. Browser sites generally do not work offline at all.

Ad load and how ads interrupt

Not all advertising is equally bad for solving. A banner below the grid is easy to ignore. A full-screen video between puzzles is annoying but predictable. An interstitial that appears mid-solve, or one triggered by tapping a hint, is genuinely disruptive if you are holding a chain of deductions in your head. Test by finishing two puzzles and noting whether any ad arrives while you are solving rather than between them.

Sync across devices

If you solve on a phone and a laptop, check whether progress, statistics and unfinished puzzles carry across. Sync almost always requires an account, a fair trade if you use it and pure overhead if you do not. Some apps sync stats but not an in-progress grid, the combination most likely to disappoint.

Accessibility and grid legibility

Givens and your own entries should be visibly different in weight or color, not only in shade. Candidate digits should be large enough to read without squinting, which is where most apps fail on a phone. Check for dark mode and for text scaling if you use it system-wide. For anyone with color vision differences, check that highlighting and conflict marking do not rely on color alone, and if you use a screen reader, sudoku support is uneven enough to be worth testing first.

Keyboard and touch input

On a desktop, good keyboard input means number keys place a digit, a modifier or dedicated key toggles candidate mode, and arrow keys move the selection. Reaching for the mouse on every candidate is the commonest reason browser sudoku feels slow. On a phone, the pattern that works is selecting a cell then tapping a digit from a number pad below the grid, with a visible candidate toggle. The pattern that does not is a keypad that pops over the grid and hides the row you are reasoning about.

Printing

If you ever solve on paper, check what happens when you print. A well-built page prints a clean grid with no ads, no navigation, and lines heavy enough to survive a home printer. A badly built one prints the whole web page, ad slots included. Many solving-focused sites have no print path at all, which is the gap generator sites fill.

Does it teach, or only serve puzzles?

Some apps include real technique guides covering singles, pairs, pointing sets and X-Wing, and connect the hint system to them. Most do not. If you are past easy puzzles and want to get better rather than just keep playing, an app that teaches beats one with a larger catalog.

What "free" actually costs you

Four models dominate, and knowing which one you are in tells you what to expect.

Ad-supported. Genuinely free, paid for by advertising and usually by data used to target it. The cost to you is attention plus whatever the privacy policy permits.

Ad-supported with a one-off removal purchase. The same app with a permanent unlock. The friendliest model in the category, because the free version is complete rather than crippled and the paid one has no recurring cost.

Subscription. Recurring payment for an ad-free experience, harder difficulties, an archive, or unlimited hints. Worth it if you solve daily, poor value otherwise. Check what happens to your statistics and saved puzzles if you stop paying.

Freemium hints and lives. The pattern borrowed from casual mobile games: hints are a consumable, earned slowly, watched-for, or bought. This deserves specific caution in sudoku, because it creates an incentive to make you want hints, which pushes against honest difficulty grading. Check that the "hard" tier is genuinely solvable by logic without them.

Whichever model you land in, the five-minute test is the same. Solve two puzzles at a level you know. Watch where the ads appear, ask for one hint and read what it says, turn auto-candidates off and see whether the app still feels good, and print one grid. That tells you more than any roundup, including this one.

Frequently Asked Questions

Is there a genuinely free sudoku app with no ads? Yes, mostly in the open-source category, where apps carry no advertising or tracking and generate puzzles on the device. The trade is a plainer interface and usually no tutorial content. Some commercial apps also sell a one-off ad removal, which is not free but has no recurring cost.

Are browser sudoku sites as good as installed apps? On a desktop with a keyboard, often yes, and lean single-purpose sites can beat app-store apps because they are built by solvers. On a phone, installed apps generally win on touch input and offline play, the two things browsers handle worst.

Does using hints and auto-candidates make you worse at sudoku? Not worse, but it changes what you practice. Auto-candidates remove the bookkeeping half of the skill, and cell-filling hints remove the deduction that was about to happen. If improving matters, keep auto-candidates off and prefer hints that name the technique.

Why do difficulty ratings vary so much between apps? There is no shared standard. Some grade by counting givens, some by the hardest technique their solver needs, some by how long users take. A puzzle labeled hard in one app can be medium in another, so calibrate against a single source rather than comparing labels.