JSON Formatter

Understanding JSON: Format Rules, Common Errors, and Best Practices

JSON (JavaScript Object Notation) is the most widely used data interchange format on the web. Created by Douglas Crockford in the early 2000s, it is human-readable, lightweight, and natively supported by every major programming language.

JSON Syntax Rules

• Data types: strings, numbers, booleans (true/false), null, objects, and arrays.
• Strings must use double quotes. Single quotes are not valid: "name" not 'name'.
• Keys must be strings (in double quotes). No unquoted keys.
• No trailing commas: {"a": 1, "b": 2,} is invalid.
• No comments: JSON does not support // or /* */ comments.
• Numbers cannot have leading zeros: 07 is invalid, use 7.

Common JSON Errors and Fixes

JSON vs. Other Formats

Formatting and Minification

Pretty-printing adds indentation (typically 2 or 4 spaces) and line breaks to make JSON readable during development. Minification removes all whitespace to reduce file size for production. A 50KB pretty-printed JSON file might shrink to 30KB when minified - a 40% reduction that improves load times.

Best Practices

• Use camelCase for keys in JavaScript environments, snake_case in Python/Ruby APIs.
• Keep nesting shallow - deeply nested JSON is hard to read and parse.
• Use arrays for ordered collections and objects for named properties.
• Validate JSON before sending it to APIs. A single syntax error causes the entire payload to be rejected. Our JSON formatter validates and pretty-prints in one step.
• Use ISO 8601 format for dates: "2026-04-05T12:00:00Z".