Shadow library

Shadow libraries are online databases of readily available content that is normally obscured or otherwise not readily accessible. Such content may be inaccessible for a number of reasons, including the use of paywalls, copyright controls, or other barriers to accessibility placed upon the content by its original owners. Shadow libraries usually consist of textual information as in electronic books, but may also include other digital media, including software, music, or films.

Examples of shadow libraries include Anna's Archive, Library Genesis, Sci-Hub and Z-Library, which are popular book and academic shadow libraries and may be the largest public libraries for books and literature.