The Text Encoding Initiative (TEI) is one of the longest-lived and most influential projects in the field now known as the Digital Humanities. Its purpose is to provide guidelines for the creation and management in digital form of every type of data created and used by researchers in the Humanities, such as source texts, manuscripts, archival documents, ancient inscriptions, and many others. As its name suggests, its primary focus is on text rather than sound or video, but it can usefully be applied to any form of digital data. Crucially, it was created and is maintained by the scholarly community for the use of that community.