The computer revolution changed every facet of our lives, including litigation. Though computer interfaces are designed to display information through familiar renderings of everyday physical objects, computer files are stored and behave differently from their physical counterparts. Metadata, the information contained in a computer file that are almost invisible to users, can profoundly affect the admissibility and authenticity of digital files. This paper explains what metadata are and the role they play in litigation to authenticate other evidence or as evidence in itself. This paper proposes a new best practice for attorneys: whenever a lawyer receives an electronic file or hard drive from a client, the attorney should immediately back up and forensically image it so that the metadata are preserved.