Lost media refers to any type of media that is believed to no longer exist in any form, or for which no copies can be found, even in part. This term mainly includes visual, audio, or audiovisual media, such as films, television shows, radio broadcasts, music, and video games.

Many television and radio broadcasts were recorded on magnetic tape. These tapes were often erased as part of industry practices. Motion picture studios also destroyed original nitrate film copies because film and broadcast material was often seen as temporary and not valuable after they made money. Some media that is considered lost might still be in studio or public archives. However, these items may not be available to the public due to copyright rules, donor restrictions, or because people are not interested in outdated programs or topics.

All media formats, such as films, tapes, phonograph records, CDs, Blu-ray discs, DVDs, and digital data stored on devices like USB flash drives, SD cards, solid-state drives, and hard disk drives, naturally deteriorate over time. This happens especially if they are not stored properly.

To prevent the loss of these works, preservation efforts usually involve storing them in archives.

Lost films

A large part of silent films created in the United States are now lost. A 2013 report from the United States Library of Congress says that 70 percent of these films are completely lost.

Lost television broadcasts

Most lost television broadcasts are early programs that cannot be found in studio archives or personal collections. Many lost broadcasts are lost because of intentional destruction, such as a method used in the early days of television called wiping, or because they were not properly cared for. The earliest television shows were live broadcasts that were never recorded at all because there were no recording devices or people wanted to record them back then.

Lost music

The Library of Congress believes that many of the earliest musical recordings from the late 19th century to the early 20th century are no longer available. For example, only 2% of the more than 3,000 wax cylinders made by the North American Phonograph Company between 1889 and 1894 are in the National Recording Preservation Board's sound recording library as of 2024.

A related idea is "lostwave," a term created online to describe recordings that still exist but have little or no information about their creators or origins. Some examples of lostwave, such as "Subways of Your Mind" and "Ulterior Motives," were identified in 2024 after being studied by people online working together.

Lost video games

Video games, including those bought as digital downloads, can disappear when digital game stores shut down. Examples include the Wii Shop Channel, Xbox Live Arcade, V Cast Network, and the Nintendo eShop. A preview of the unreleased game Silent Hills, called P.T., could no longer be downloaded after it was removed from the PlayStation Network within one year. Digital games Dodge Club Party and Dodge Club Pocket for the Wii U and Nintendo 3DS were taken off the Nintendo eShop in 2019 and 2022 and became unavailable to the public because of problems beyond Nintendo’s control.

According to the Video Game History Foundation, 87% of video games made in the United States before 2010 are no longer available for purchase outside of illegal sources or unauthorized sellers. Many of these games are at risk of being lost or already have been. Some fans believe that publishers have a responsibility to keep games available to honor the creators and players. People who preserve video games, such as groups like the Video Game History Foundation and individual hobbyists, work to save video game history that might otherwise be lost. This effort is driven by the belief that these games have cultural and historical value or can serve as educational resources for future generations. Factors that threaten game preservation include old storage materials, digital stores closing, or issues related to rights or money.

Lost electronic data

Data stored in electronic computers can be lost if it is not regularly moved to newer file formats. This occurs because as new computer systems and technologies are created, older systems may stop working over time, making the data inside them impossible to access. Keeping electronic data safe is made harder by the fact that without an emulator for a specific computer system that can read the data, the original information might become unusable when the original hardware fails. In some cases, the data might still be recovered through detailed work to understand the original system well enough to decode as much data as possible.

To help protect important information, the Arctic World Archive has been selected to store code from public websites like GitHub. This archive also holds a variety of data important to many companies, organizations, and governments, such as the constitutions of Brazil and Norway.

Media shared online, such as files, live streams, and blog posts, is especially at risk of being lost. Media that is only available on streaming services without a physical copy is sometimes removed, making it impossible to access without copying it, which can sometimes lead to illegal activity. The Electronic Frontier Foundation describes this as a new type of lost media that is only saved by people who take the effort to create and keep copies, even if doing so could lead to serious legal problems.