National Science Digital Library

National Science Digital Library (NSDL) of the United States is an open-access online digital library and collaborative network of disciplinary and grade-level focused education providers operated by the Institute for the Study of Knowledge Management in Education.

NSDL's mission is to provide quality digital learning collections to the science, technology, engineering, and mathematics (STEM) education community, both formal and informal, institutional and individual.

Their work is based on user data, disciplinary knowledge, and participation in the evolution of digital resources as major elements of effective STEM learning.

[5] NSDL also provides access to services and tools that enhance the use of this content in a variety of contexts.

[6] NSDL is designed primarily for K-16 educators, but anyone can access NSDL.org and search the library at no cost, and without creating a user account, although some content providers require a nominal fee or subscription to retrieve their specific resources.