Diplomatics is forensic palaeography.

Specifically, diplomatics is a branch of study that seeks clues as to the provenance of written documents, especially handwritten documents. It seeks to validate or disconfirm the alleged origin and authenticity of written documents by studying:

• the materials upon which they were written;
• the penmanship and alphabets or other scripts used in them;
• the language and style of language they were written in, including their vocabulary, usage, and literary style.

The name diplomatics was first coined for this science by the Benedictine monk Jean Mabillon, who in 1681 published his six volume treatise De re diplomatica (Latin: roughly, "The Study of Documents"). Mabillon began studying old documents with a view towards establishing their authenticity or falsity as a result of his investigations into doubts that had been raised as to the authenticity of Merovingian documents from the cathedral of St Denis in Paris by the Jesuit Daniel Papebroek. During the Middle Ages, the production of spurious charters and other documents was common, either to provide written documentation of existing rights or to bolster the plausibility of claimed rights. After Mabillon's work, a livelier awareness of the potential for forged or spurious documents became much more important, both for students of history and of law.

The study of diplomatics is important for history, to determine whether alleged historical documents are in fact true or forgeries. For the same reason, diplomatics occasionally comes into play in law. Some famous cases involving diplomatics issues include:

• Lorenzo Valla's proof of the forgery of the Donation of Constantine;
• The Hitler diaries hoax.

See also: false document