Kriol is spoken as a first or second language by over 20,000 indigenous people across the north of Australia from the Gulf of Carpentaria in the East to the Kimberley area in the West, and from Darwin (North) to Tennant Creek (South). Like other English-lexified creole languages of the Pacific, Kriol originates in the English-based pidgin used between the first colonizers and the indigenous inhabitants of the Sydney area, which subsequently spread inland and north. Many authors assume that creolization occurred abruptly early in the 20th century at an Anglican mission at Roper River (close to the present-day Ngukurr) through children from different language backgrounds who had been brought together in dormitories; for this reason Kriol is often referred to as Roper River Kriol. There is however evidence that the pidgin had already stabilized and linguistically expanded at that time, due to the need for communication between the increasing numbers of Aboriginal people working on cattle stations, the (primarily) English-speaking pastoralists, and the non-English-speaking (e.g. Chinese) colonists in a wider area. Kriol is mainly used in oral communication and only has a limited role in other domains.
While the lects spoken at Roper River and nearby Bamyili (Barunga) remain the best documented, the description in APiCS (default lect) aims to be representative of all documented lects. In addition to Roper River Kriol these include Kriol spoken in the township of Katherine, Westside Kriol spoken in the northern Victoria River District, and Kimberley Kriol further west around Fitzroy Crossing and Halls Creek. These varieties mostly do not exhibit differences with respect to the APiCS features; where they do, this is stated explicitly (e.g. Roper River Lect). The region is also indicated for each example.