Codelists are key to making activity and organisation data from different social and technological actors comparable.

Codes are used to represent many standard values in a universe of discourse. For example, codelists such as Country or Currency ensure that different actors have unambiguous, comparable definitions (e.g. BE = Belgium; NL = Netherlands) they can use when defining and exchanging data.

Codelists are updated through a managed process, as illustrated by the IATI Codelist Management for the IATI codelists.

An important advantage is that the codes in codelists are independent of the language used.
This is illustrated by the codelists of the Belgian register of legal entities and the #tag pivot.

The IATI codelists illustrate the wide domain that can be covered by codelists. Once defined, most codelists are reusable across domains.

The codelists in the list below are included because of their role in requirements engineering cases.