JSON Formatter, Validator & Beautifier

What is JSON?

JSON (JavaScript Object Notation) is a lightweight, text-based format for storing and exchanging structured data. It was derived from JavaScript object syntax but is now language-independent — every major programming language can parse and generate it. JSON is the default data format for REST APIs, web application configuration files, browser storage (localStorage), and most modern databases and cloud services.

A JSON file is any plain-text file containing valid JSON data, typically with a .json extension. Common examples include package.json (Node.js project settings), tsconfig.json (TypeScript configuration), and API response bodies saved to disk for debugging or testing.

JSON syntax: objects, arrays, and square brackets

JSON has two container types that are easy to confuse:

• Objects { } — curly braces: a collection of key-value pairs. Keys must be double-quoted strings. Example: {"name": "Alice", "age": 30}
• Arrays [ ] — square brackets: an ordered list of values. Values can be any JSON type — strings, numbers, booleans, nulls, objects, or other arrays. Example: ["red", "green", "blue"]

The most common confusion is using square brackets when you need curly braces or vice versa. Use [ ] when you have a list of things; use { } when you have named properties. Arrays and objects can be nested freely: {"colors": ["red", "green"]} is an object with an array value.

Pretty-print vs. minify

Pretty-printing (formatting) adds consistent indentation and newlines to make JSON human-readable — useful for debugging, reviewing API responses, and reading configuration files. Minifying strips all whitespace to produce the most compact representation, which reduces payload size when transmitting JSON over a network. The data is identical either way; only the whitespace differs.

JSON escaping

The escape action converts a JSON string into a version safe for embedding inside another JSON string literal — double quotes become \", backslashes become \\, and control characters are replaced with their escape sequences (\n, \t, etc.). This is useful when building JSON-in-JSON payloads or serializing JSON for storage in a database field. Unescape reverses the process.

Common JSON validation errors

• Trailing commas — JSON does not allow a comma after the last item in an array or object (unlike JavaScript). {"a": 1,} is invalid.
• Single quotes — JSON requires double quotes for all strings and object keys. {'key': 'value'} is invalid.
• Comments — JSON has no comment syntax. Both // and /* */ cause parse errors.
• Unquoted keys — all object keys must be quoted strings. {key: "value"} is invalid.
• Non-finite numbers — Infinity, -Infinity, and NaN are not valid JSON values.

JSON5 and JSONC

If your configuration file uses comments or trailing commas, it is likely JSON5 or JSONC (JSON with Comments) rather than strict JSON. These formats extend JSON syntax for human-authored files and require their own parsers — they are not valid standard JSON and will fail with a standard JSON.parse() call.

Frequently asked questions