Bluebook

The Bluebook: A Uniform System of Citation is a style guide that prescribes the most widely used legal citation system in the United States. It is taught and used at a majority of law schools in the United States and is also used in a majority of federal courts. Legal publishers also use several "house" citation styles in their works. The Bluebook is compiled by the Harvard Law Review, Columbia Law Review, Yale Law Journal, and University of Pennsylvania Law Review. Currently, it is in its 22nd edition (published May 2025). Its name was first used for the 6th edition (1939). Opinions have differed regarding its origins at Yale and Harvard Law Schools, with the latter long claiming credit. The Supreme Court uses its own unique citation style in its opinions, even though most of the justices and their law clerks obtained their legal education at law schools that use The Bluebook. Furthermore, many state courts have their own citation rules that take precedence over the guide for documents filed with those courts. Some of the local rules are simple modifications to The Bluebook system.