An orphan work is a copyright-protected work for which rightsholders are positively indeterminate or uncontactable. Sometimes the names of the originators or rightsholders are known, yet it is impossible to contact them because additional details cannot be found. A work can become orphaned through rightsholders being unaware of their holding, or by their demise (e.g. deceased persons or defunct companies) and establishing inheritance has proved impracticable. In other cases, comprehensively diligent research fails to determine any authors, creators or originators for a work. Since 1989, the amount of orphan works in the United States has increased dramatically since some works are published anonymously, assignments of rights are not required to be disclosed publicly, and registration is optional and, thus, many works' statuses with respect to who holds which rights remain unknown to the public even when those rights are being actively exploited by authors or other rightsholders.
Precise figures of orphan works are not readily available, even though libraries, archives and museums hold a vast number of them. In April 2009, a study estimated that the collections of public sector organisations in the UK held about 25 million orphan works. Examples of orphan works include photographs that do not note the photographer, such as photos from scientific expeditions and historical images, old folk music recordings, little known novels and other literature. Software which becomes an orphaned work is usually known as abandonware. In 2015, the Computerspielemuseum Berlin estimated that around 50% of their video game collection consisted of at least partial orphans. Source code escrow can prevent software orphaning but is seldom applied.
In countries whose laws do not specifically allow for the use of orphan works, orphan works are not available for legal use by filmmakers, archivists, writers, musicians or broadcasters.