JSON Formatter & Validator
Paste your JSON data below to format, validate, and beautify it instantly. You can also minify JSON to reduce file size. All processing happens in your browser — your data is never sent to any server.
What Is JSON?
JSON (JavaScript Object Notation) is a lightweight data interchange format that is easy for humans to read and write, and easy for machines to parse and generate. It was derived from JavaScript but is now used across virtually all programming languages. JSON has become the de facto standard for data exchange on the web, powering APIs, configuration files, and data storage.
JSON Syntax Rules
Understanding JSON syntax is essential for working with web APIs and modern applications:
- Objects are enclosed in curly braces
{}and contain key-value pairs separated by commas - Arrays are enclosed in square brackets
[]and contain ordered lists of values - Keys must be strings enclosed in double quotes (single quotes are not valid JSON)
- Values can be strings, numbers, booleans (
true/false),null, objects, or arrays - No trailing commas are allowed after the last element in an object or array
- No comments are supported in standard JSON
Common JSON Errors
When working with JSON, these are the most frequent mistakes developers encounter:
- Using single quotes instead of double quotes for strings and keys
- Trailing commas after the last property in an object or array
- Unquoted keys — all keys in JSON must be wrapped in double quotes
- Using undefined — JSON only supports
null, notundefined - Including comments — standard JSON does not allow
//or/* */comments
Why Format JSON?
Raw JSON from APIs often comes as a single line of text, making it nearly impossible to read. Formatting (also called "pretty printing") adds proper indentation and line breaks, making the structure visible at a glance. This is invaluable for debugging API responses, reviewing configuration files, and understanding data structures.
JSON vs XML
JSON has largely replaced XML for web data exchange because it is more compact, easier to read, and faster to parse. While XML supports attributes, namespaces, and comments, JSON's simplicity makes it the preferred choice for REST APIs, mobile applications, and modern web development.