CiteSeer was the first digital library and search engine to provide automated citation indexing and citation linking by autonomous citation indexing.

CiteSeer was developed in 1997 at the NEC Research Institute, Princeton, New Jersey, by Steve Lawrence, Lee Giles and Kurt Bollacker. The service transitioned to the Pennsylvania State University's College of Information Sciences and Technology in 2003. Since then, the project has been led by Professor Lee Giles.

After serving as a public search engine for nearly ten years, CiteSeer, originally intended as a prototype only, began to scale beyond the capabilities of its original architecture. Since its inception, the original CiteSeer grew to index over 750,000 documents and served over 1.5 million requests daily, pushing the limits of the system's capabilities. Based on an analysis of problems encountered by the original system and the needs of the research community, a new architecture and data model was developed for the "Next Generation CiteSeer," or CiteSeer^x, in order to continue the CiteSeer legacy into the foreseeable future.