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Free online JSON Formatter tool. Supports JSON beautification, validation, minification, and JSON tree visual editing. Built-in syntax error detection and auto-repair. Supports code conversion to 13 programming languages (TypeScript/Java/Python/Go/Rust/Swift/Kotlin/C#/C++/PHP/MySQL/YAML/XML). Ideal for API debugging, configuration inspection, and log reading.
Paste your JSON content into the editor to instantly beautify it. Great for viewing API responses, configuration files, and log fields. The tool automatically adds indentation and line breaks, organizing compact data into a clear hierarchical structure. It defaults to 2-space indentation; you can also switch indent size in the toolbar.
JSON Formatter is better suited for content that is already valid but hard to read. JSON Repair is better suited for fixing invalid structures like errors, missing quotes, and trailing commas. If formatting reports an error, we recommend doing JSON Repair first. In short: formatting only adjusts layout without changing content; repair attempts to fill in missing quotes/brackets and remove extra commas to make it valid JSON again.
Usually because the content isn't valid JSON — for example, it contains comments, single quotes, trailing commas, or unclosed brackets. The JSON specification (RFC 8259) requires keys to use double quotes, strings cannot use single quotes, there must be no comma after the last element, and // or /* */ comments are not allowed. In this case, it's better to do JSON Repair first, then format.
Absolutely. API responses, Webhook data, analytics logs, and config snippets often need formatting before troubleshooting. The tool also supports JSON tree view visual editing, mind map view, and code conversion to 13 programming languages, helping you quickly understand data structures.
Yes. The tool supports converting JSON to TypeScript/Java/Python/Go/Rust/Swift/Kotlin/C#/C++/PHP/MySQL/YAML/XML — 13 formats in total. One-click generation of corresponding code structures, perfect for quickly generating frontend and backend data models from API responses.
No. All formatting, validation, minification, and code conversion runs entirely locally in your browser. Data is never uploaded to any server. It's safe even when processing API responses containing secrets, tokens, or user privacy. Data is cleared when you close the page.
Yes. The tool uses virtual scrolling rendering and Web Worker background parsing. JSON files of several megabytes can be smoothly formatted and browsed without freezing the page. For very large files, we recommend uploading the JSON file directly rather than pasting, for more stable performance.
Minification removes all unnecessary spaces and line breaks from JSON, producing the most compact single-line result. This significantly reduces size, saves bandwidth and storage, and is commonly used for API transmission, writing configurations, embedding in code, or as environment variables. Minified JSON is semantically identical to formatted JSON; it's just not human-readable.
Tree View renders JSON as a collapsible hierarchical tree, supporting expand/collapse nodes and visual field editing, suitable for browsing deeply nested data. Mind Map View presents the structure as connected nodes, visually showing parent-child relationships between objects and arrays, suitable for mapping out complex data structures or giving presentations.
Yes. The tool provides a key sorting feature that supports rearranging object keys in ascending or descending alphabetical order, making it convenient for comparing differences between two JSONs, standardizing config file field ordering, or displaying API fields in a fixed order for Code Review.
Yes. The tool supports compressing and encoding the current JSON content into a URL to generate a shareable link. Recipients can open the link to see the same data without uploading to a server, great for quick collaboration on API issue troubleshooting or reproducing data scenarios.
JSON (JavaScript Object Notation) is a lightweight data interchange format that uses key-value pairs and arrays to represent data. Due to its simplicity, readability, and cross-language nature, it has become the de facto standard for Web APIs, configuration files, logs, and frontend-backend data transmission. JSON has only six basic value types: string, number, boolean, null, object, and array. Its syntax rules are jointly defined by RFC 8259 and ECMA-404.
JSON formatting (also called JSON beautification) is the process of adding proper indentation and line breaks to compact JSON without changing data content, organizing it into a hierarchical structure that is easy for humans to read. JSON in API responses, logs, and storage is often compressed into a single line, making it very difficult to read directly. After formatting, you can clearly see object nesting, array elements, and the value of each field.
The opposite operation to formatting is JSON minification, which removes all non-essential whitespace characters, converting JSON back to its most compact single-line form to reduce transmission size. Formatting and minification are a pair of reversible operations; neither changes JSON semantics, only affecting readability and size.
JSON validation checks whether a piece of text conforms to JSON syntax rules. Common invalid patterns include: using single quotes instead of double quotes, keys without quotes, trailing commas after the last element, containing // or /* */ comments, and incorrectly closed brackets or quotes. None of these are valid JSON, and formatting will report errors — in this case, you should use the JSON Repair tool first, then format.
Building on formatting, this tool also provides Tree View, Mind Map View, and code conversion to 13 programming languages: you can collapse JSON into a visual hierarchical tree to browse deep structures, or one-click convert API response JSON into TypeScript interfaces, Java classes, Python dictionaries, or database table creation statements for direct use in development. All processing is done locally in the browser; data is never uploaded to servers.
JSON has only six value types. Understanding them helps quickly determine whether data is valid and how to map to programming language types.
| Type | Example | Description |
|---|---|---|
string | "hello" | String, must use double quotes, supports escape characters and \uXXXX Unicode encoding. |
number | 25 / 3.14 / -1e5 | Number, supports integers, decimals, and scientific notation; parsed as double-precision float, no distinction between integer and float. |
boolean | true / false | Boolean, can only be lowercase true or false. |
null | null | Null value, representing no data; must be lowercase, different from empty string or 0. |
object | {"k": "v"} | Object, a collection of key-value pairs wrapped in curly braces; keys must be double-quoted strings. |
array | [1, 2, 3] | Array, an ordered list of values wrapped in square brackets; elements can be of different types. |
The following characters in JSON strings must be escaped with a backslash; otherwise parsing will fail.
| Escape | Meaning |
|---|---|
\" | Double quote |
\\ | Backslash |
\/ | Forward slash (optional escape) |
\n | Newline |
\r | Carriage return |
\t | Tab |
\b | Backspace |
\f | Form feed |
\uXXXX | Unicode character represented by four hexadecimal digits |
Below are commonly encountered invalid JSON patterns and their valid forms, for reference when formatting reports errors.
| Invalid | Valid | Note |
|---|---|---|
{name: "a"} | {"name": "a"} | Keys must use double quotes |
{'name': 'a'} | {"name": "a"} | Strings must use double quotes, not single quotes |
{"a": 1,} | {"a": 1} | Trailing commas are not allowed |
{"a": 1} // comment | {"a": 1} | JSON does not support comments |
{"a": undefined} | {"a": null} | There is no undefined; use null for null values |
{"a": .5} | {"a": 0.5} | Decimals must have an integer part 0 |
The third parameter of browser and Node.js built-in JSON.stringify specifies indentation, the most common programmatic way to format JSON.
const data = { name: '张三', age: 25, tags: ['a', 'b'] };
// Beautify: third parameter is indentation spaces (can also pass '\t' for Tab)
const pretty = JSON.stringify(data, null, 2);
console.log(pretty);
// Minify: omit the third parameter to get the most compact single line
const mini = JSON.stringify(data);
console.log(mini); // {"name":"张三","age":25,"tags":["a","b"]}
// Parse string to object (validates syntax, throws SyntaxError if invalid)
const obj = JSON.parse(pretty);Python's standard library json uses indent and ensure_ascii parameters to control indentation and Chinese character display.
import json
data = {"name": "张三", "age": 25, "tags": ["a", "b"]}
# Beautified output, indent specifies indentation, ensure_ascii=False preserves Chinese
pretty = json.dumps(data, indent=2, ensure_ascii=False)
print(pretty)
# Minified output: use the most compact separators
mini = json.dumps(data, separators=(",", ":"), ensure_ascii=False)
print(mini)
# Parse string (throws json.JSONDecodeError if invalid)
obj = json.loads(pretty)jq is a powerful command-line tool for processing JSON, enabling quick beautification, minification, and field extraction.
# Beautify (default 2-space indent) cat data.json | jq '.' # Minify to single line cat data.json | jq -c '.' # Extract a specific field cat data.json | jq '.user.name' # Directly pipe curl results for beautification curl -s https://api.example.com/user | jq '.'
All JSON formatting, validation, minification, and code conversion in this tool runs entirely locally in your browser. Data is never uploaded to any server, nor recorded or cached remotely. It is safe even when processing API responses containing secrets, tokens, or user information. Data is cleared when you close or refresh the page.
Most likely caused by single quotes, keys without double quotes, or containing // or /* */ comments. The JSON specification requires all strings and keys to use double quotes, and comments are not supported. Please switch to double quotes and remove comments, or use the JSON Repair tool first.
Usually caused by incorrectly closed brackets {} or [] or quotes, resulting in incomplete JSON. Check that structures are properly paired and closed. When pasting API responses, you may have copied only partial content — ensure you copy completely.
JSON does not allow commas after the last element of an object or array; for example {"a":1,} or [1,2,] are invalid. Remove the extra comma. JavaScript objects allow trailing commas, but JSON does not — be especially careful when copying from code.
This is JSON's Unicode escape notation, which is inherently valid and can still be parsed normally after formatting. If you prefer to display Chinese directly, disable escaping on the generating side (e.g., Python's ensure_ascii=False, Go's disable HTML escaping).
JSON numbers are parsed as IEEE 754 double-precision floats. Integers exceeding 2^53 (e.g., snowflake IDs, order numbers) lose precision. The solution is to wrap large integers as strings during transmission, i.e., "id": "9007199254740993", to avoid being parsed as numbers.
Simply switch to "Minify" to convert beautified multi-line JSON back to the most compact single line for API transmission, writing configurations, or embedding in code. Minification and beautification are inverse operations and do not change data content.