XML stands for Extensible Markup Language and is a markup language. XML serves as a ‘set of rules’ for encoding documents in a serialized format that is both machine and human readable. The standards are defined in the XML 1.0 specification . They are used, for example, in sog. XML RPCs (Remote Procedure Calls). Currently, they have mostly been replaced by the more modern JSON.

Similar markup languages are JSON and YAML.