Why JSON Won the API War
For decades, XML (eXtensible Markup Language) was the heavy, verbose standard for APIs (SOAP). However, REST APIs overwhelmingly shifted to JSON for two critical performance reasons:
1. **Payload Size**: XML requires opening and closing tags for every single node (e.g., `<name>John</name>`). JSON uses lightweight key-value syntax (`"name":"John"`). This drastically reduces the byte size of data transferred over the wire.
2. **Parsing Velocity**: Browsers parse JSON natively using highly optimized C++ `JSON.parse()` routines directly into memory arrays and objects. Parsing XML requires traversing a complex Document Object Model (DOM) tree, which consumes significantly more CPU cycles.
Minification for Edge Environments
When transmitting JSON over a network, human readability is irrelevant. Stripping whitespace, line breaks, and indentation from JSON payloads (minification) before transit can reduce the file size by 15-30% depending on the nesting depth.
In high-traffic edge APIs, this size reduction directly translates to lower egress bandwidth costs and faster client-side rendering times.