If you run out of puzzles you can import the following Sudoku collections:

OpenSudoku

 

• 100 Easy Puzzles
• 100 Medium Puzzles
• 100 Hard Puzzles
• 100 Very Hard Puzzles

Civiliza's Collection

 

• 724 Starter Puzzles
• 30 Easy Puzzles
• 189 Medium Puzzles
• 35 Hard Puzzles
• 22 Very Hard Puzzles

Andoku Collection

 

As the legal owner of the original Andoku app, I can offer you hundreds of the original Andoku puzzles including squiggly/jigsaw puzzles here:

 

• Andoku Puzzles

qqwing Collection

• 1000 simple puzzles

• 1000 easy puzzles

• 1000 intermediate puzzles

• 1000 expert puzzles

Sudocue Collection

• The No-Trick Ponies Collection (250 puzzles)

• The Learning Curve Collection (2500 puzzles)

• The Superiors Collection (160 puzzles)

• The Almost Daily Nightmare Collection (400 puzzle)

• Snowflake Puzzles (100 puzzles)

• Top 10000 Sudokus (10000 puzzles ;-)

gnome-sudoku Collection

• gs4 easy (100 puzzles)

• gs4 medium (100 puzzles)

• gs4 hard (100 puzzles)

• gs4 very hard (100 puzzles)

• gs5 easy (100 puzzles)

• gs5 medium (100 puzzles)

• gs5 hard (100 puzzles)

• gs5 very hard (100 puzzles)

• gs6 easy (100 puzzles)

• gs6 medium (100 puzzles)

• gs6 hard (100 puzzles)

• gs6 very hard (100 puzzles)

Beyond Nightmare

These are the toughest of the toughest puzzles from the Sudoku Player's Forum. They are all rated >=10.1 by Sudoku Explainer and beyond anything you'll find in a newspaper, a magazine or any Sudoku app. For the most addicted players only.

 

• 4593 Beyond Nightmare Puzzles