Sudoku Royale vs Mind The Frog Sudoku: Notes, Undo and Levels

Both apps have six difficulty levels, but they spend them differently. Sudoku by Mind The Frog runs from "easy" to "diabolical", with automatic and manual notes, undo and redo, up to ten grids in progress and play on or offline; it is free with ads and a one-time Remove Ads purchase at $1.99. Sudoku Royale runs from Easy to Extreme, has no ads and nothing to buy, and teaches the techniques its top levels need, but it has no automatic notes and no undo. If you want a fast, no-frills tool that fills candidates for you, Mind The Frog is the better fit. If you want to learn to solve the hard grids yourself, Royale is.

The App Store facts

From each app's US App Store listing, checked October 26, 2026. Prices and paid items change, so check the listing before you buy.

Mind The Frog has been on the App Store since 2010, which makes it one of the older sudoku apps on the store, with 38,659 US ratings against Royale's 11. Its last update was June 20, 2025. It is also tiny: the listing says it "doesn't eat up a lot of storage", and at 6 MB it is the smaller download (Royale is 43 MB).

Feature by feature

Automatic notes against learning to see candidates

This is the real fork between the two apps. Mind The Frog lists "automatic and manual notes": you can let the app write the candidates for every cell and spend your time eliminating, which is how many experienced players like to work through diabolical grids. Combined with undo and redo, you can try a line of reasoning and back out of it cleanly.

Sudoku Royale has no automatic candidates. You write notes yourself, and the app clears them from the row, column and box when you place a number. That is more work on a fresh Extreme grid, and some players will find it a reason to stay with Mind The Frog. The trade is that spotting candidates is the skill the app is trying to build. The Journey teaches one technique per chapter, and the Dojo drills patterns like naked pairs and X-Wing until you see them without writing every candidate down. Our guide to sudoku apps with notes compares how other apps handle pencil marks.

Diabolical and Extreme

Neither app defines its top level by technique in its listing, so a direct comparison of "diabolical" and "Extreme" is not possible from the outside. What can be said: Royale's Master and Extreme unlock only after a number of solves at the level below, and its hardest puzzles call for techniques such as XY-Wing and Swordfish. Mind The Frog's listing does not mention unlocking levels, and a developer reply on its App Store page says every difficulty level has been free since version 3.7, after a reviewer complained that the harder ones were paid.

Ads and the paid version

Mind The Frog shows a banner ad in the free app; a version note says it was "separated from interactive elements" so you do not tap it by accident. Remove Ads costs $1.99, once. The developer also says in a review reply that it has always offered a separate paid, ad-free version of the app with a similar icon, so check which one you are buying. Sudoku Royale has no ads, no purchases and no subscription to compare against either.

A no-distraction app, two ways

Mind The Frog's listing is built around getting out of your way: no lengthy intros or slow animations, big buttons that avoid fat-fingering, and it plays your music and nothing else. Royale is quiet in a different sense: no ads, no pop-ups, separate toggles for music and sound, and it respects Reduce Motion. It does have more around the grid (Daily Challenge, Belts, optional live games), and a timer in the corner that cannot be hidden. If you want nothing but the grid, Mind The Frog is the plainer of the two.

Where Mind The Frog is the better pick

• You want automatic candidates. Royale has none.
• You rely on undo and redo. Mind The Frog lists both; Royale has neither.
• You juggle several puzzles. Up to ten grids can be in progress.
• Storage or simplicity matters. It is a very small app with almost nothing beyond the puzzle.
• You want full offline play. Its listing says on or offline without qualification.

Where Sudoku Royale is the better pick

• No ads without paying. There is no unlock to buy.
• Hints that teach. In Practice, a hint names the technique and the cell and links to its lesson. Mind The Frog's listing mentions no hints.
• A path to the top levels. Lessons, drills and a coach that picks positions from your own games.
• A daily puzzle with friends. The Daily Challenge ranks you against friends and the world.

Which should you choose?

If you already solve diabolical puzzles and want automatic notes, undo and a small, fast app, Mind The Frog is hard to beat, and its ad removal is a single purchase. If you are working your way up and want the app to help you understand each step, without paying anything, try Sudoku Royale. For more options, see the Mind The Frog alternatives, the best sudoku apps for advanced players and every matchup on the comparisons page.