JSON: The Universal Data Format

JSON (JavaScript Object Notation) has become the default data interchange format for web APIs, configuration files, and data storage. Its success comes from simplicity: just six data types (string, number, boolean, null, array, object) and a syntax that is both human-readable and machine-parseable. Every major programming language has built-in or standard-library JSON support, making it the lingua franca of modern software.

Common JSON Pitfalls

Trailing commas are the most frequent JSON syntax error — valid in JavaScript but illegal in JSON. Comments are not allowed in standard JSON (though JSON5 and JSONC extensions support them). Keys must be double-quoted strings — single quotes and unquoted keys are invalid. Numbers cannot have leading zeros (01 is invalid) or trailing decimal points (1. is invalid). These strict rules make JSON unambiguous to parse but occasionally frustrating to write by hand.

JSON Performance Considerations

JSON.parse() in modern browsers processes roughly 1 GB/second, making it fast enough for most applications. However, for very large payloads, streaming parsers (like JSONStream in Node.js) process data incrementally without loading the entire string into memory. For binary-heavy data, consider MessagePack or Protocol Buffers — they are 2-5x smaller and faster to parse than equivalent JSON, though they sacrifice human readability.