How to Format JSON

JSON (JavaScript Object Notation) is the most widely used data format in web development. APIs return it, configuration files store it, and databases serialize it. But raw JSON from an API is often minified — a single, unreadable line of text. Formatting JSON makes it human-readable and dramatically easier to debug.

What Is JSON?

JSON is a lightweight, text-based data interchange format. It is language-independent but uses conventions familiar to programmers of C, JavaScript, and Python. JSON represents data as key-value pairs and ordered lists.

A minimal JSON object looks like this:

{"name":"Alice","age":30,"active":true}

After formatting, the same data becomes:

{
  "name": "Alice",
  "age": 30,
  "active": true
}

Common JSON Formatting Issues

Minified responses. Most APIs return compact JSON without whitespace to reduce payload size. This is great for performance but terrible for debugging.
Missing commas. A forgotten comma between properties is the most common syntax error in hand-edited JSON.
Trailing commas. Standard JSON does not allow trailing commas after the last property in an object or array. This trips up developers coming from JavaScript.
Unquoted keys. JSON requires property names to be double-quoted strings. Writing { name: "Alice" } is invalid — it must be { "name": "Alice" }.
Single quotes. JSON only allows double quotes for strings. Single quotes will cause a parse error.