Sudoku Royale vs Stress Free Sudoku: Timer, Undo and Ads

Stress Free Sudoku is made for relaxed solving: its listing promises no timers and no penalties, full undo, a dual keypad for answers and pencil marks, and 200,000 puzzles across five levels. It is free, its age rating notes advertising, and its listing shows no purchase to remove the ads. Sudoku Royale has no ads at all and teaches harder techniques, but it is the less relaxed of the two in two ways that matter here: a timer you cannot hide, and no undo. If a clock in the corner spoils sudoku for you, Stress Free is the better app, and we would rather say so than have you find out after downloading ours.

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.

Boy Howdy Technology has published Stress Free Sudoku since 2013, and it has 10,395 US ratings. Sudoku Royale arrived in 2026 with 11 so far.

Calm play, feature by feature

The timer question

Stress Free Sudoku's listing is blunt: "No timers at all!" A reviewer quoted on its page says it is the first app they found without a timer or penalties for a wrong number. That is the whole idea of the app, and it delivers on it.

Sudoku Royale shows a clock in the corner during Practice, and there is no setting to hide it. Nothing happens when it runs: there is no countdown and no mistake limit in Practice, and a puzzle you leave picks up where you stopped. But if seeing the minutes tick is what makes sudoku feel like work, that is a real drawback. Our sudoku apps without a timer page lists the apps that let you switch it off.

Undo and checking

Stress Free lists full undo and a "check your work" button, and a version note adds a setting to always check. So you can play like paper, check only when you are unsure, or have errors flagged as you go. Conflicts between numbers, and between pencil marks, are highlighted unless you turn that off.

Sudoku Royale makes one choice for you: every number is checked the moment you place it, and a wrong one is rejected. That rules out building ten moves on a mistake, which is its own kind of calm, but there is no undo and no way to play unchecked. Read how to find mistakes in sudoku if you prefer to hunt them down yourself.

Entering numbers and notes

The dual keypad is Stress Free's signature: one row of keys places answers and another places pencil marks, so you never toggle a mode. Reviewers on its page praise it for keeping taps to a minimum. Pencil marks erase themselves as you enter answers, with an option to keep them.

Sudoku Royale uses a single number bar with a Notes toggle, and offers several ways to use it: tap a cell then a number, arm a number and tap cells (see number-first vs cell-first), or hold a number key and swipe along the bar, plus slide-to-select on the grid. Notes clear themselves from the row, column and box when you place a number. Neither app fills in candidates automatically.

Ads

Stress Free's age rating says it contains advertising, and the listing shows no in-app purchase at all, so there is no way to pay them away. Reviewers describe a banner at the bottom of the screen, and one says there are no pop-up or video ads, which suits a calm app. Sudoku Royale has no ads, no in-app purchases and no subscription, and its privacy label has no "Data Used to Track You" section; Stress Free's does.

Where Stress Free Sudoku is the better pick

• You want no timer. Royale's cannot be hidden.
• You want undo. Stress Free lists full undo; Royale has none.
• You want to decide when work is checked. A button, an always-on setting, or nothing at all.
• You like a separate keypad for notes. No mode switching.
• A bottom banner does not bother you. Then it costs nothing.

Where Sudoku Royale is the better pick

• No ads at all. Not even a banner, and nothing to buy.
• Room to grow past Genius. Master and Extreme call for techniques like X-Wing and XY-Wing, and the Journey teaches them one chapter at a time.
• Hints that teach. The hint names a technique, such as a hidden single, and points at the cell rather than revealing the digit.
• A daily puzzle. Stress Free's listing does not mention one; Royale's Daily Challenge has streaks and an archive.

Which should you choose?

For the calmest possible game, with no clock, undo and a banner ad you can ignore, Stress Free Sudoku is the honest recommendation. If no ads matters more than no timer, or you want to get better at hard puzzles, get Sudoku Royale. Related reading: the best relaxing sudoku apps, Stress Free Sudoku alternatives and all head-to-heads on the comparisons page.