Validate, beautify, and minify JSON instantly in your browser. Syntax errors are highlighted with line numbers. Nothing is sent to a server.
JSON (JavaScript Object Notation) is a lightweight, human-readable data interchange format. It is the dominant format for REST API responses, configuration files, and data serialization in web development. Raw JSON from APIs is often returned as a single line with no whitespace — compact for transmission but unreadable for humans. A JSON formatter (also called a JSON beautifier) parses the raw string and re-serializes it with consistent indentation, making the structure immediately legible.
JSON has a strict specification (ECMA-404). Common syntax errors that cause parse failures include: trailing commas after the last element in an object or array (allowed in JavaScript but illegal in JSON), single-quoted strings (JSON requires double quotes), unquoted keys, comments (JSON has no comment syntax), and undefined values (JSON supports only null, not JavaScript's undefined). This tool uses the browser's native JSON.parse() to validate and reports the exact error message for any syntax failure.
Beautify (format) adds newlines and indentation to produce a human-readable multi-line string. Use this when debugging API responses or editing configuration files. Minify removes all optional whitespace to produce the most compact string. Use this to reduce payload size in HTTP responses or localStorage — minified JSON can be 20–40% smaller than its formatted equivalent for deeply nested objects.
Every major REST API — GitHub, Stripe, Shopify, OpenAI, Twitter/X — returns JSON by default. Understanding JSON structure is foundational to web development. When building or testing an API integration, paste the raw response into this formatter to inspect the data structure before writing any parsing code. This saves significant debugging time and makes schema discovery immediate. Encode or decode Base64 data fields from API payloads with our Base64 encoder online. URL-encoded query strings within JSON values can be decoded with our URL encoder.
The most common causes are: (1) Trailing commas — {"a":1,} is invalid JSON. (2) Single quotes — JSON requires double quotes for strings and keys. (3) Comments — JSON has no comment syntax; // comment or /* comment */ are invalid. (4) Unquoted keys — {name: "John"} is JavaScript object syntax, not valid JSON. The error message from this validator will point to the exact character position of the failure.
JSON is a text format that is a strict subset of JavaScript literal syntax. JSON always requires double-quoted keys and string values, has no undefined, no functions, no comments, and no trailing commas. A JavaScript object is an in-memory data structure. JSON.parse() converts JSON text to a JS object; JSON.stringify() converts a JS object to JSON text.
Yes. This tool runs entirely in your browser. The JSON you paste never leaves your device and is never sent to any server. You can safely paste API credentials, configuration secrets, or production data to inspect them — though as a general security practice, avoid pasting production secrets into any third-party tool unnecessarily.
There is no hardcoded limit — it is bounded only by your browser's JavaScript memory. In practice, JSON.parse() handles files up to several hundred megabytes without issue in modern browsers. For very large files (500 MB+) consider using a dedicated desktop tool like jq in your terminal.
Use json_encode($array) to convert a PHP array to a JSON string, and json_decode($json, true) to parse a JSON string into a PHP associative array. Pass JSON_PRETTY_PRINT as the second argument to json_encode() for formatted output: json_encode($data, JSON_PRETTY_PRINT).