BookCrossing (also known as BC, BCing or BXing) is defined as the practice of leaving a book in a public place to be 'caught' by others, who may then do likewise.

The term is derived from bookcrossing.com, a free online book community which was founded in 2001 to encourage the practice, aiming to "make the whole world a library."

The community aspect of BookCrossing.com has grown and expanded in ways which were not expected at the outset, in the form of blog or forum discussions, mailing lists, and holding annual conventions throughout the world.

Business partners and co-founders Bruce and Heather Pedersen[2] collaborated with Hornbaker to launch BookCrossing.com on April 21, 2001.

BookCrossing.com users can 'go hunting', where a member will go to the website to view a list of books that have recently been "released", then go to the location it was left to "catch" it.

Books may also be left at "Official BookCrossing Zones" (OBCZs), which are in certain coffee shops, cafes, and restaurants, or other public places.