JSON Formatter & Validator

What Is JSON?

JSON (JavaScript Object Notation) is a lightweight data format used to store and exchange information between systems. It is the standard format for APIs, configuration files, data storage, and communication between web servers and browsers. If you work with web development, APIs, or any kind of data processing, you will encounter JSON regularly.

JSON structures data using key value pairs and supports nested objects and arrays. A simple example looks like this: {“name”: “John”, “role”: “developer”, “active”: true}. In practice, JSON responses from APIs can be hundreds or thousands of lines long, often delivered as a single compressed line with no formatting, which makes them nearly impossible to read without a tool like this one.

How to Use This Tool

Paste your JSON into the input field and click Format. The tool parses the JSON, validates its syntax, and outputs a cleanly indented, readable version. If the JSON contains errors (missing brackets, trailing commas, unquoted keys), the tool will identify the problem and show you where the syntax breaks.

You can also minify formatted JSON back to a single line, which is useful when you need compact JSON for API requests or configuration files.

All processing happens in your browser. Your data is not sent to any server.

Common JSON Errors

Trailing commas. JSON does not allow a comma after the last item in an object or array. This is one of the most frequent mistakes, especially if you are used to writing JavaScript where trailing commas are valid.

Unquoted keys. Every key in JSON must be wrapped in double quotes. Single quotes are not valid in JSON, even though they work in JavaScript.

Single quotes around strings. JSON requires double quotes for all strings. {“name”: ‘John’} is invalid. {“name”: “John”} is correct.

Missing brackets or braces. When working with deeply nested JSON, it is easy to lose track of opening and closing brackets. This tool highlights the exact position where the structure breaks.

Comments. JSON does not support comments. If you have added // or /* */ comments to a JSON file, they need to be removed before the file will parse correctly. Some configuration tools (like VS Code’s settings.json) allow comments in JSON-like files, but standard JSON does not.

When You Need a JSON Formatter

Debugging API responses. When an API returns a wall of minified JSON, formatting it makes the structure visible so you can find the data you need or identify what is missing.

Writing configuration files. Many tools and platforms use JSON for configuration. Formatting helps you see the structure clearly and catch errors before they cause problems.

Validating data. Before sending JSON to an API or importing it into a database, validating the syntax prevents errors downstream.

Comparing data. Formatted JSON with consistent indentation is much easier to compare visually or with a diff tool than minified JSON.