Why is JSON the standard response format for REST APIs?

JSON (JavaScript Object Notation) has become the de facto standard for REST API responses for several reasons. It is human-readable — easier to debug than XML or binary formats. It is lightweight with minimal syntax overhead compared to XML. It natively maps to data structures in virtually every programming language (objects, arrays, strings, numbers, booleans, null). JavaScript (the dominant web language) parses it natively with JSON.parse(). Most HTTP client libraries (axios, requests, fetch) handle JSON serialization/deserialization automatically. JSON also supports deeply nested structures that naturally represent domain objects. Always set Content-Type: application/json in responses and validate that the body is valid JSON before returning it.