General Sudoku Sites:
* Sudoku.com: [https://sudoku.com/](https://sudoku.com/) - A comprehensive site with a wide range of difficulty levels, daily puzzles, and even a puzzle generator.
* Web Sudoku: [https://www.websudoku.com/](https://www.websudoku.com/) - A classic and user-friendly site that offers various difficulty settings and tracking of your progress.
* Sudoku.org: [https://www.sudoku.org/](https://www.sudoku.org/) - Another great option with a focus on different puzzle variations and difficulty levels.
* Logic Puzzles: [https://logic-puzzles.com/](https://logic-puzzles.com/) - This site features a wide variety of logic puzzles, including Sudoku, KenKen, and more.
Newspapers and Magazines:
* The New York Times: [https://www.nytimes.com/games/sudoku/](https://www.nytimes.com/games/sudoku/) - Offers daily Sudoku puzzles along with other games.
* The Guardian: [https://www.theguardian.com/crosswords/sudoku](https://www.theguardian.com/crosswords/sudoku) - Features a variety of Sudoku puzzles with different difficulty levels.
Apps:
* Sudoku by Conceptis: [https://apps.apple.com/us/app/sudoku-by-conceptis/id404449268](https://apps.apple.com/us/app/sudoku-by-conceptis/id404449268) - Available on iOS and Android, this app offers a huge library of puzzles with different difficulty levels.
* Sudoku by the Numbers: [https://apps.apple.com/us/app/sudoku-by-the-numbers/id967773495](https://apps.apple.com/us/app/sudoku-by-the-numbers/id967773495) - Another popular app with a user-friendly interface and plenty of puzzles to choose from.
No matter your preference, you're sure to find a free Sudoku puzzle that suits your skill level and interests!