What is JSON?
JavaScript Object Notation, a lightweight text format for representing structured data, supported natively by every modern language.
JSON is the lingua franca of web APIs. Six data types (string, number, boolean, null, array, object) are enough to encode almost any tree-shaped data, and the syntax is small enough to parse with a 200-line state machine. That tradeoff (small grammar, broad coverage) is why JSON beat XML for API payloads in the early 2010s and never gave the territory back.
In practice you never write a JSON parser. Every language ships one, JSON.parse in JS, json.loads in Python, serde_json in Rust, encoding/json in Go, and the rough edges (huge integers, NaN, dates) come from corner cases the spec doesn't cover.
JSON Schema, JSON-LD, and JSONL extend the format for validation, semantic linking, and streaming respectively. Each is just JSON with conventions layered on top, same parsers, same tooling.
In the wild
{"name": "Stripe", "domain": "stripe.com"}[{"id": 1}, {"id": 2}], an array of objects{"colors": ["#635BFF", "#0A2540"]}