ToolMight LogoToolMight

JSON Formatter & Validator

Format, validate, and beautify JSON instantly with this free online JSON formatter and validator. Paste any raw API response, configuration file, or nested data structure to pretty print JSON with 2-space indentation, minify for production, or auto-fix common syntax errors like trailing commas and unquoted keys. All processing runs entirely client-side in your browser — your data never touches a server.

Loading Tool...

Learn About This Tool

Why use a JSON formatter?

Raw JSON from API responses and log files is typically compressed onto a single line, making it nearly impossible to read or debug. A JSON formatter parses the data and re-outputs it with proper indentation, line breaks, and aligned braces so you can visually trace the structure at a glance.
  • Convert single-line API payloads into readable, indented output
  • Spot missing brackets, misplaced commas, and structural issues instantly
  • Share formatted JSON snippets with teammates in pull request reviews
  • Prepare configuration files for deployment with consistent formatting

Pretty print JSON with proper indentation

Paste your JSON into the editor and click the Format button to pretty print it with 2-space indentation. The tool uses JSON.stringify(data, null, 2) under the hood, producing output identical to what you'd get in Node.js or a browser console. For encoded payloads, decode them first with our Base64 Decoder before formatting.
  • 2-space indentation matching standard JavaScript conventions
  • Nested objects and arrays are properly aligned and collapsible
  • Output preserves Unicode characters and escape sequences exactly
  • Copy or download the formatted result as a `.json` file

Minify JSON for production

Click the `Minify` button to strip all whitespace, line breaks, and indentation from your JSON. Minified JSON is typically 30-60% smaller than formatted output, which reduces network transfer times for API responses and saves storage in databases or localStorage. For example, a 2KB formatted payload often compresses to under 800 bytes after minification.
  • Removes all unnecessary whitespace and newlines
  • Reduces payload size for faster API responses and network transfers
  • Word wrap automatically enabled so you can read the single-line output
  • Ideal for embedding JSON in environment variables or URL parameters

Common JSON syntax errors and how to fix them

When validation fails, the editor highlights the exact line and column where the error occurs. The most frequent issues are trailing commas, single quotes, and unquoted keys — all of which the Fix JSON button can repair automatically. If your JSON originates from a JWT token, decode it first with our JWT Decoder to extract the payload before formatting.
  • Trailing commas: `{"name": "Jane",}` — removed automatically by Fix JSON
  • Single quotes: `{'name': 'Jane'}` — converted to double quotes
  • Unquoted keys: `{name: "Jane"}` — wrapped in double quotes
  • Missing commas: `{"a": 1 "b": 2}` — commas inserted between values
  • Smart quotes from word processors: `“name”` — replaced with standard `"`
  • Comments: `// note` and `/* block */` — stripped to produce valid JSON

JSON, JSONC, and JSON5: what's the difference?

Standard JSON (RFC 8259) does not allow comments, trailing commas, or single-quoted strings. JSONC (JSON with Comments) is used by VS Code configuration files and allows `//` and `/* */` comments. JSON5 goes further by permitting single quotes, unquoted keys, trailing commas, and hex numbers. This tool accepts all three variants: paste JSONC or JSON5 and use `Fix JSON` to convert it into strict, standards-compliant JSON that any parser can read.
  • JSON: strict double quotes, no comments, no trailing commas
  • JSONC: adds single-line and multi-line comment support
  • JSON5: adds single quotes, unquoted keys, trailing commas, and hex values
  • Fix JSON strips comments and normalizes syntax to produce valid JSON

Format JSON programmatically in code

If you need to format JSON inside your application rather than using an online tool, both JavaScript and Python have built-in methods. In JavaScript, use JSON.stringify(data, null, 2) to produce indented output. In Python, use json.dumps(data, indent=4, sort_keys=True). From the command line, you can pipe JSON through python3 -m json.tool input.json for quick formatting without writing a script.
  • JavaScript: `JSON.stringify(obj, null, 2)` — 2-space indented output
  • Python: `json.dumps(obj, indent=4)` — 4-space indented output
  • CLI: `python3 -m json.tool data.json` — format from terminal
  • Node.js: `cat data.json | npx json` — quick pipe formatting

Inspect and analyze JSON structure

After formatting, the stats panel displays key metrics about your JSON structure: file size in KB, total number of keys, and maximum nesting depth. These stats help you understand the complexity of API responses or configuration files at a glance. For tabular data that started as a spreadsheet, convert it first with our CSV to JSON Converter.
  • File size displayed in KB for quick payload assessment
  • Total key count helps estimate object complexity
  • Maximum nesting depth reveals how deeply structured the data is
  • Large files (2MB+) are processed in a Web Worker to prevent UI freezing

How to Use JSON Formatter & Validator

1

Paste your JSON into the editor

Open the tool and paste your JSON string into the main editor panel labeled `Source.json`. The editor immediately validates your input — a green `Valid` badge appears for correct JSON, or a red `Invalid Syntax` badge with the exact line and column number if errors are found.

2

Fix syntax errors (if any)

If the editor shows `Invalid Syntax`, look for the `Fix JSON` button in the bottom toolbar (it appears only when errors are detected). Click it to automatically repair trailing commas, single quotes, unquoted keys, smart quotes, and missing brackets. The input editor updates in place with the corrected JSON.

3

Format or minify your JSON

Click `Format` to beautify the JSON with 2-space indentation and proper line breaks, or click `Minify` to compress it into a single line with all whitespace removed. Both buttons are in the bottom toolbar of the input panel. The result appears in the `Output` tab automatically.

4

Review the output and stats

Switch to the `Output` tab to see the result in a read-only editor. Below the editor, the stats panel shows the file size, total key count, and maximum nesting depth. Use the `Wrap` toggle in the header to enable word wrap for long minified lines.

5

Copy or download the result

Click the `Copy` button in the output panel header to copy the formatted or minified JSON to your clipboard. To save it as a file, click the `Download` button — it exports a `formatted.json` file to your device.

Code Implementations

Copy & paste production-ready code snippets for JSON Formatter & Validator in your language of choice

File: format_json.py
Python
import json

def format_json(raw_json_str):
    parsed = json.loads(raw_json_str)
    return json.dumps(parsed, indent=4)

raw = '{"name":"John","age":30,"city":"New York"}'
print(format_json(raw))

Frequently Asked Questions

JSON (JavaScript Object Notation) is a lightweight text-based data format used to exchange structured data between applications. It supports six data types: strings (`"hello"`), numbers (`42`, `3.14`), booleans (`true`, `false`), `null`, objects (`{}`), and arrays (`[]`). JSON is the standard format for REST APIs, configuration files, and web application data exchange.
A JSON formatter takes raw or minified JSON and reorganizes it with consistent indentation (typically 2 or 4 spaces), line breaks after each key-value pair, and aligned braces and brackets. It also validates syntax and highlights errors at the exact line and column where they occur. This tool uses `JSON.stringify(data, null, 2)` internally to produce standard 2-space indented output.
Yes. This tool runs entirely in your browser using client-side JavaScript. No JSON data is transmitted to or stored on any server. You can verify this by opening your browser's Network tab — no requests are made when you format or validate JSON. This makes it safe for API keys, tokens, and internal configuration data.
Minification removes all whitespace, line breaks, and indentation to produce the smallest possible valid JSON string. For example, a 2,400-byte formatted payload typically reduces to around 800 bytes after minification. This is ideal for API responses, localStorage values, and URL parameters where size matters. If your JSON is embedded in an authentication token, decode it first with our JWT Decoder.
The `Fix JSON` button appears when your input contains syntax errors. It automatically repairs trailing commas (`{"a": 1,}`), converts single quotes to double quotes (`'key'` → `"key"`), wraps unquoted keys in double quotes (`name:` → `"name":`), removes JavaScript-style comments, replaces smart quotes from word processors, inserts missing commas between values, and balances unclosed brackets. The corrected JSON replaces your input so you can then format or minify it.
Yes. Files over 1MB are automatically processed in a Web Worker thread so the editor remains responsive. The practical limit depends on your device's available memory — most modern browsers handle files up to 50-100MB without issues. For files larger than 2MB, the stats panel skips the deep structure analysis to maintain performance.
The most common causes are: keys without double quotes (`{name: "Jane"}`), trailing commas after the last item (`{"a": 1,}`), single quotes instead of double quotes (`{'name': 'Jane'}`), JavaScript comments (`// comment`), and unescaped special characters inside strings. The error message shows the exact line and column number. Try the `Fix JSON` button to resolve most of these automatically.
Standard JSON (RFC 8259) does not allow comments. However, JSONC (JSON with Comments), used by VS Code settings files, supports `//` single-line and `/* */` multi-line comments. If you paste JSONC into this tool, the `Fix JSON` button strips all comments to produce valid standard JSON. Minifying also removes any comments automatically.
Validation checks whether the JSON syntax is correct — that all brackets are balanced, keys are double-quoted, and values use proper types. Formatting (pretty printing) takes valid JSON and adds indentation and line breaks for readability. This tool performs both: it validates on paste and formats on click. Invalid JSON cannot be formatted until the syntax errors are fixed.
Use `JSON.stringify(data, null, 2)` where the third argument controls the number of indentation spaces. For example: `const formatted = JSON.stringify({name: "Jane", age: 30}, null, 2)` produces a string with 2-space indentation. To minify, omit the third argument: `JSON.stringify(data)`. This is the same method this online tool uses internally.
Use `json.dumps(data, indent=4, sort_keys=True)` from Python's built-in `json` module. The `indent` parameter sets the number of spaces, and `sort_keys=True` alphabetizes keys. From the command line, run `python3 -m json.tool input.json` to format a file without writing a script.
Paste the nested JSON into the editor and click `Format`. The tool indents each level by 2 spaces, making parent-child relationships visible through alignment. After formatting, check the stats panel — the `Depth` value tells you how many levels deep the nesting goes. For example, `{"user": {"address": {"city": "NYC"}}}` has a depth of 3.
JSON uses braces, brackets, and double quotes for structure, making it unambiguous for machines but verbose for humans. YAML uses indentation instead of braces and supports comments, making it popular for configuration files like Docker Compose and Kubernetes manifests. JSON is the standard for API payloads and data exchange, while YAML is preferred for human-edited config files. Both can represent the same data structures.
JSON arrays use square brackets and can contain any mix of values: `[1, "hello", true, null, {"key": "value"}, [1, 2, 3]]`. Paste your array into the editor and click `Format` — each element gets its own line with proper indentation, making it easy to scan large datasets. Arrays of objects (common in API responses) are formatted with each object's opening brace on a new line.
Yes. Press `Ctrl+Enter` (or `Cmd+Enter` on Mac) to format the current input, `Ctrl+F` to search within the editor, and `Ctrl+L` to clear the input. These shortcuts work in both the input and output panels.

Related tools

JWT Decoder

Popular

Decode and inspect JWT tokens securely.

Base64 Encoder / Decoder

Popular

Encode or decode Base64 strings instantly.

CSV to JSON Converter

Popular

Convert CSV sheets to structured JSON arrays.

URL Encoder / Decoder

Percent-encode or decode URL strings.

Deep Dives & Guides

Master this tool with our expert tutorials and best practices.

3 min readArticle

How to Format and Validate JSON Instantly

A comprehensive guide on formatting and validating JSON payload in your browser without compromising privacy. Learn about JSON best practices, security, and schema validation.

Read Full Guide