OER are teaching, learning, and research materials in any medium—digital or otherwise—that reside in the public domain or have been released under an open license that permits no-cost access, use, adaptation, and redistribution by others with no or limited restrictions. OER eliminate cost barriers for students and allow unrestricted, immediate access to learning materials, increasing the likelihood for students to complete their courses successfully. The Libraries Alt-Textbook project provides grants and ongoing support for faculty to adopt, adapt, or create low-cost alternatives to expensive textbooks.