JSON Formatter, Converter and Validator
Paste your JSON to format, validate, convert to CSV or XML, or minify it in one click. The formatter shows syntax errors with line number and error description. The JSON to CSV converter maps each object in an array to a row with keys as column headers. All processing runs in your browser with no data sent to any server. Free, no signup, works with any JSON from REST API responses to configuration files.
How to use the JSON formatter and validator
- 1
Paste your JSON into the input panel
Paste your JSON into the input panel on the left. It accepts raw, minified, or partially broken JSON regardless of current validity.
- 2
Click Beautify or press Ctrl+Enter
Click Beautify or press Ctrl+Enter to format with 4-space indentation and syntax highlighting applied immediately.
- 3
View the formatted output
View the formatted output on the right with color-coded keys, strings, numbers, booleans, and null values for easy reading.
- 4
Copy to clipboard or download
Copy to clipboard or download as a .json file with one click. No signup needed and nothing is stored on any server.
What this JSON tool includes
Live validation
Instantly shows Valid or Invalid as you type, with the exact line number and error description when the JSON contains problems.
Syntax highlighting
Keys, strings, numbers, booleans, and null values are rendered in distinct colors so the structure is easy to scan at a glance.
Keyboard shortcuts
Ctrl+Enter beautifies your JSON instantly. Ctrl+Shift+M minifies it. No need to reach for the mouse during editing.
CSV and XML conversion
Convert JSON arrays to CSV or XML with a single tab switch. Each object becomes a row in CSV or a set of nested tags in XML.
Minify mode
Strip all whitespace and line breaks to reduce payload size by 20 to 40% with no change to the data structure.
Private by design
All processing runs in the browser using JavaScript. Nothing is ever sent to a server, making it safe for sensitive or proprietary data.
How to format and validate JSON in your browser
Paste your JSON into the formatter and click Beautify. The tool instantly indents the code with 4-space indentation, applies syntax highlighting to keys, strings, numbers, and booleans, and shows a Valid or Invalid badge in real time. If the JSON contains errors, the formatter displays the exact line number and a description of the problem so you can fix it without guessing.
No software installation is needed and nothing is sent to a server. The formatter works with JSON from REST API responses, configuration files, log output, and any other source. For a deeper look at working with JSON data, the complete JSON guide covers the full range of JSON operations with examples.
Common JSON errors and how to fix them
The most frequent JSON errors are trailing commas after the last key-value pair or array item, single quotes instead of double quotes around strings or keys, unquoted keys, missing commas between pairs, and mismatched curly or square brackets. JSON is stricter than JavaScript object syntax and does not allow comments or undefined values.
Keys must always be in double quotes. Values must be strings in double quotes, numbers, booleans, null, arrays, or objects. The validator above shows the exact line where the error occurs. If you need to find or replace patterns within JSON values, the regex tester lets you test patterns against any text including JSON strings.
When to use JSON minification vs pretty printing
Use pretty printing while developing so the data is human-readable when you inspect network responses or configuration files. Use minification before deploying static JSON assets or sending API responses where bandwidth matters. Removing all whitespace typically reduces file size by 20 to 40% with no change to the data.
Most build tools including webpack and Vite can minify JSON automatically as part of a build step. Use the Minify tab above for quick one-off minification without setting up a build pipeline. Keep a formatted version in source control and only minify the production output so the file remains editable.
Frequently asked questions about JSON formatting and conversion
What is JSON and what is it used for?
JSON (JavaScript Object Notation) is a lightweight text format for storing and exchanging data. It is the standard format for REST API responses, configuration files, and data storage in web applications. JSON is human-readable and easy to parse in any programming language, making it the most widely used data interchange format on the web.
How do I validate JSON online?
Paste your JSON into the formatter above and click Format JSON. The tool instantly checks the syntax and shows a Valid or Invalid badge. If there are errors, the line number and error description appear so you can fix them. No signup is required and no data is sent to any server.
What are the most common JSON syntax errors?
The most common errors are trailing commas after the last item in an object or array, single quotes instead of double quotes, unquoted object keys, missing commas between key-value pairs, and mismatched brackets. JSON does not allow comments, undefined values, or JavaScript-specific features like functions or NaN.
What is the difference between JSON and a JavaScript object?
JSON is a text format that looks similar to a JavaScript object literal, but has stricter rules. JSON requires all keys to be in double quotes, does not allow trailing commas, and only supports strings, numbers, booleans, null, arrays, and objects as values. JavaScript objects can have unquoted keys, functions, undefined, and Symbol values.
How do I minify JSON for production?
Click the Minify tab above, paste your JSON, and click Minify. The tool removes all whitespace and line breaks to produce a compact single-line string. This typically reduces file size by 20 to 40%. For automated minification, most build tools like webpack, Rollup, and Vite can minify JSON files as part of the build process.
How do I convert JSON to CSV?
Click the JSON to CSV tab, paste a JSON array where each element is an object, and click Convert. The tool uses the object keys as column headers and each object as a row. The output can be copied or downloaded as a .csv file. Arrays with inconsistent keys are handled by filling missing values with empty cells.
What is JSON Schema and how is it different from JSON?
JSON Schema is a vocabulary for describing the structure, types, and constraints of JSON data. Regular JSON is just data. JSON Schema is itself valid JSON that describes what valid data looks like. It is used to validate API request and response bodies, generate documentation, and enforce data contracts between services.
How do I handle special characters in JSON strings?
Special characters in JSON strings must be escaped with a backslash. Common escape sequences are: \" for double quotes, \\ for backslash, \n for newline, \t for tab, \r for carriage return, and \uXXXX for Unicode characters. If you paste a string with unescaped special characters the validator will flag the line where the error occurs.
What is the maximum size of a JSON file?
The JSON specification does not define a maximum size. In practice, the limit depends on the parser and the environment. Most browsers can parse JSON files of several hundred megabytes. Server-side parsers often impose limits, and many REST APIs cap request and response bodies at 1 to 10 MB. For very large datasets, consider streaming parsers or splitting the data into multiple requests.
Why does JSON require double quotes instead of single quotes?
The JSON specification, defined in RFC 8259, explicitly requires double quotes for strings and keys. Single-quoted strings are valid in JavaScript but not in JSON. This strict rule ensures that JSON is language-agnostic and can be parsed consistently by any JSON library in any programming language without ambiguity.