JSON Formatter and Validator

What is JSON?

JSON stands for JavaScript Object Notation. It is a text format used to exchange structured data between applications, APIs, configuration files, and browser storage. Despite the name, many programming languages can read and write JSON.

JSON can contain objects, arrays, strings, numbers, booleans, and null. Property names and string values must use double quotes. Comments, trailing commas, undefined, NaN, and Infinity are not part of strict JSON.

How to use this formatter

1. Paste JSON into the input editor.
2. Choose two-space or four-space indentation.
3. Select Format JSON for readable output or Minify JSON for compact output.
4. If validation fails, review the browser's error and approximate line and column when available.
5. Copy the valid result or download it as a JSON file.

Formatting and minification explained

Formatting adds spaces and line breaks so nested data is easier for a person to read. It does not intentionally change the values or structure represented by valid JSON. Minification removes unnecessary formatting whitespace to create a smaller text representation.

Both operations first parse the input with the browser's native JSON.parse() function. Valid data is then serialized with JSON.stringify(). The tool never passes your input to eval() and does not execute pasted text as JavaScript.

Common JSON syntax errors

• Using single quotes instead of double quotes.
• Leaving a trailing comma after the last property or array item.
• Missing a comma between two properties.
• Leaving a string, object, or array unclosed.
• Adding JavaScript comments to strict JSON.
• Using JavaScript-only values such as undefined, NaN, or Infinity.

Syntax validation is not schema validation

This tool confirms whether text follows JSON syntax. It does not know the business rules expected by a particular API or application. For example,{"email":123} is valid JSON syntax even when an API requires the email value to be a string.

Schema validation checks required fields, allowed values, and data types for one particular system. That requires a schema or specification and is outside this version of the formatter.

Privacy and browser limits

Processing happens locally in the current browser tab. The tool accepts up to 1,000,000 input characters and 256 nesting levels to reduce the chance that unusually large or deeply nested data freezes a browser, especially on a mobile device.

Avoid pasting passwords, access tokens, personal data, or production secrets into any tool unless you understand the environment and your organization's data-handling policy. Keeping the work in the browser reduces network exposure, but copied text, downloads, browser extensions, screenshots, and device access still matter.

Important limitations

• Native parser error wording differs between browsers, so line and column guidance is best-effort.
• Duplicate object keys may not be reported; a native parser generally keeps the final value.
• Very large integers can lose precision when represented as JavaScript numbers. Store exact large identifiers as strings.
• Invalid JSON is not automatically repaired because silent fixes could change the intended data.
• The tool does not fetch JSON from a URL or call an API.

Frequently asked questions

Can a JSON document start with an array?

Yes. Objects and arrays are common top-level values, but strict JSON can also contain a top-level string, number, boolean, or null.

Does minifying JSON compress it?

Minification removes formatting whitespace. It can reduce text length, but it is not the same as ZIP, gzip, or another compression format.

Is my JSON uploaded?

No. Parsing, formatting, minifying, copying, and file creation happen in your browser. Downloading creates a temporary local file URL and then releases it.

Need website or integration help?

Clean JSON syntax is only one part of a dependable integration. Yellow Solutions can help design APIs, connect business systems, validate data, build secure web applications, and diagnose unreliable workflows.