Data types that can be expressed in JSON include: integers, strings, boolean, arrays, objects, and null. Objects in JSON syntax are denoted by simple hierarchical nesting.
The most general use case of JSON is retrieving data from a source to display inside an application. The source can be a typical HTTP web server, an external REST API, an IoT device, or any other web-based service. XMLHttpRequest and other Ajax-style methods are often used to perform the retrieval of JSON data in an asynchronous or real-time manner.
The official MIME type for JSON is application/json, while ".json" is the universally recognized file extension.