Magnetic tape provides a cost-effective way to retain the exponentially increasing volumes of data being created in recent years. The low cost per terabyte combined with tape’s low energy consumption make it an appealing option for storing infrequently accessed data and has resulted in a resurgence in use of the technology. Magnetic tape as a digital data storage technology was first commercialized in the early 1950’s and has evolved continuously since then. Despite its long history, tape has significant potential for continued capacity and data rate scaling. This article strives to provide an overview of linear magnetic tape technology, usage, history, and future outlook. After a short introduction, the article delves into the details of how modern tape drives and media operate, including the basic mechanism and physics of magnetic recording, current tape media technology, state-of-the-art tape head technology, tape layout and encoding, data retrieval, timing-based servo and mechatronics of a tape drive, and the capabilities of current drives. This is followed by a discussion of tape libraries, an overview of tape library performance modeling research, operating system-level and application-level tape support, tape use cases, and the future scaling potential and outlook of tape. The article concludes with a history of tape hardware, media, usage and software.