ULF Sudoku — Play Free Sudoku Online

Welcome to ULF Sudoku — a refined, fast Sudoku experience you can play on any device. Choose Easy, Medium, or Hard; toggle Zen mode for a calmer look; track your streak; and explore challenge modes like One Mistake, No Erase, and Speed Run.

How to Play Sudoku

Sudoku is a logic puzzle on a 9×9 grid divided into nine 3×3 boxes. Fill the grid so that each row, column, and 3×3 box contains the digits 1–9 exactly once.

1. Pick a difficulty in the Menu (⚙️).
2. Tap a cell, then tap a number below to place it.
3. Use ✏️ Notes to pencil in candidates without committing.
4. Undo and Erase are there if you change your mind.
5. Need help? Tap ? for a single-cell hint.

Beginner Tips

• Scan rows & columns for missing numbers; place the obvious ones first.
• Use notes to track candidates; they clear automatically when a number is placed.
• Look for singles: if a number can go in only one spot in a row/column/box, that’s your move.
• Stuck? Switch to another area or try a different technique (like “hidden singles”).

ULF Sudoku Features

• 🎯 Classic, Daily, and Challenge modes
• 📝 Smart notes and conflict highlighting
• ⏱ Timer (toggle on/off) and Speed Run mode
• 🌙 Zen mode for a distraction-free board
• 📱 PWA: install to play fast & offline
• ⭐ ULF Sudoku+ (Premium): ad-free + extra themes

FAQ

Is ULF Sudoku free?

Yes. You can play for free in your browser. Premium removes ads and adds extra themes.

How do I install it on my phone?

Use the “Install” button or your browser’s “Add to Home Screen”. The app works offline after the first load.

What are Challenge modes?

One Mistake ends your run on a single wrong entry; No Erase forbids erasing; Speed Run gives you 10 minutes to finish.

Why do I see ads?

Ads help keep the game free. You can remove them anytime by upgrading to ULF Sudoku+.

ULF Sudoku is a casual puzzle game for all skill levels. If you enjoy it, try our upcoming games on the ULF Games page (coming soon!).