Two comprehensive geometry textbooks available online are the Holt Geometry textbook, found at Dragonometry.net, and the McDougal Littell Geometry textbook found at NexusLearning.net. Both textbooks are for use in middle or high school and cover the basics of geometry as well as some more advanced concepts.
Both Dragonometry and Nexus Learning make their geometry textbooks available as PDF files. This means users must download the books to a computer before using them. The website separates the books into chapters to minimize the size of each download. Pages may be opened in a separate browser window or using the program Adobe Reader.