Json i.e. JavaScript Open Notation is a lightweight, human readable and machine parsable data format. Combined with the RESTful API respresentation, it is by far the most popular data exchange format for mobile apps. Given it’s ease of use, extensibility and speed of parsing, it trumps over the age old XML format. JSON is built on two structures: A collection of name/value pairs (E.g. Objects) or an ordered list of values (E.