Hein Online is an extensive, continuously updated source of documents in the area of (mainly U.S.) law. It offers more than 100 million pages dealing with legal history.

Hein Online is divided into individual collections (libraries), of which the most important ones are:

• Law Journal Library —1,100 titles, mostly all published volumes
• Federal Register Library—federal norms and U.S. Laws (since 1936)
• Legal Classics Library—1,200 titles
• Treaties and Agreements Library—international treaties and agreements of the US
• U.S. Supreme Court Library—collection of decisions of the U.S Supreme Court
• English Reports—English Reports (1220–1865), 178 volumes, reprint published in 1900–1932.