This JSON formatter takes raw or minified JSON and converts it into a clean, readable format with proper indentation. It also validates your JSON syntax and shows clear error messages when the input is invalid. You can choose between 2-space and 4-space indentation to match your coding style. Everything runs in your browser, so your data never leaves your device.
Enter your values to see the result.
{"name":"Alice","age":30} → { "name": "Alice", "age": 30 }
A minified object is expanded with 2-space indentation by default.
[1,2,3] → [ 1, 2, 3 ]
Arrays are formatted with one element per line for readability.
{"a":{"b":{"c":true}}} → { "a": { "b": { "c": true } } }
Nested objects are indented progressively to show the structure clearly.
JSON, which stands for JavaScript Object Notation, is the most widely used data format for web APIs and configuration files. It provides a simple, human-readable way to represent structured data using objects (collections of key-value pairs enclosed in curly braces) and arrays (ordered lists of values enclosed in square brackets). Despite its origins in JavaScript, JSON is language-independent and supported by virtually every programming language through built-in libraries.
The format enforces strict syntax rules that make it both predictable and easy to parse. All property names must be strings wrapped in double quotes. String values also use double quotes. Numbers follow standard notation without leading zeros. The literals true, false and null represent boolean and null values. Properties are separated by commas, and no trailing comma is permitted. These constraints mean that a valid JSON document can be parsed unambiguously by any compliant parser.
This JSON formatter uses the browser's built-in JSON.parse function to validate and parse your input, then JSON.stringify with an indentation parameter to produce the formatted output. The parsing step serves double duty: it validates the syntax and converts the compact representation into an internal data structure. The stringification step then walks that structure and produces a new string with proper indentation and line breaks.
When the input contains a syntax error, JSON.parse throws an exception that the tool catches and converts into a user-friendly error message. This approach means validation and formatting happen in a single step — if the output appears, your JSON is guaranteed to be valid. If an error appears instead, you know there is a syntax issue that needs to be fixed before the JSON can be used.
Developers use JSON formatters constantly when working with APIs. An API response received in a terminal or log file is often a single long line of minified JSON that is nearly impossible to read. Pasting it through a formatter reveals the structure: which fields are nested inside others, what arrays contain, and how the data is organized. This is essential for debugging API integrations and understanding response schemas.
Configuration files are another common use case. Tools like TypeScript, ESLint, VS Code and countless others use JSON for their configuration. When editing these files by hand, it is easy to introduce syntax errors like missing commas or trailing commas. Running the file through a formatter both validates the syntax and produces clean output that is easier to review in code diffs. Data engineers also use JSON formatters when inspecting data pipelines, transforming datasets, or validating the output of ETL processes.
All formatting and validation operations happen locally in your browser. Your JSON data is never sent to any server, never stored in any database, and never analyzed by any third party. The JavaScript functions that perform the parsing and formatting are part of your browser's standard library and execute in microseconds, so even large JSON documents with thousands of properties are formatted instantly without any loading time or network dependency.
JSON stands for JavaScript Object Notation. It is a lightweight data interchange format that is easy for humans to read and write, and easy for machines to parse and generate. JSON is built on two structures: a collection of name-value pairs (objects) and an ordered list of values (arrays). It has become the standard format for APIs, configuration files and data exchange between web services because of its simplicity and universal language support.
A JSON formatter takes compact or minified JSON and restructures it with proper indentation and line breaks so that the hierarchical structure becomes visually clear. Nested objects and arrays are indented to show their level of depth, making it easy to see which properties belong to which objects. This is especially useful when working with large API responses or configuration files where the structure may be deeply nested and difficult to follow in a single line.
Yes, this tool validates your JSON as it formats it. The formatting process requires parsing the JSON first, and if the parser encounters a syntax error, the tool displays a clear error message instead of a formatted result. Common errors include missing commas between properties, unmatched braces or brackets, trailing commas, unquoted property names and single quotes instead of double quotes. The error message helps you identify that something is wrong so you can fix the input.
No, all formatting and validation happens entirely in your browser using JavaScript. Your JSON is never transmitted over the network, never stored, and never processed by any third party. You can safely paste API responses, configuration files or any other JSON data containing sensitive information without any risk of the content being exposed or logged on a remote server.
Different coding standards and style guides recommend different indentation widths. JavaScript and TypeScript projects commonly use 2-space indentation, following the conventions popularized by frameworks like React and tools like Prettier. Python projects and some other ecosystems prefer 4-space indentation. This tool lets you match the indentation style of your project so the formatted output can be pasted directly into your codebase without requiring further reformatting.
Valid JSON requires double quotes around all string keys and string values. Numbers must be written without leading zeros. Boolean values must be lowercase true or false. Null values must be lowercase null. Properties must be separated by commas, and no trailing comma is allowed after the last property in an object or the last element in an array. Comments are not supported in standard JSON, so any text outside of string values that looks like a comment will cause a parsing error.
Last updated on 2026-09-26 · Written by UtiliaTools