JSON data format is used when writing JavaScript based application which includes browser extension and websites. JSON is often used as a common format for serializing and transmitting structured data in applications that communicate with each other over the Internet. It is primarily used to transmit data between a server and web application, serving as an alternative to XML.

These applications are created using different programming languages and run in very different environments. JSON is suited to this scenario because it is an open standard, it is easy to read and write, and it is more compact than other representations. RESTful web services use JSON extensively as the format for the data inside requests and responses.