FlexBook is a textbook authoring platform developed by the CK-12 Foundation launched in 2008, focused on textbooks for the K-12 market. Derived from the words "flexibility" and "textbook," a FlexBook allows users to produce and customize content by re-purposing educational content using different modules. FlexBooks can be designed to suit a learner's learning style, region, language, or level of skill, while adhering to the local education standards.