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JSON Formatter & Validator

Format, validate and beautify JSON instantly in your browser. Free online tool with syntax validation, error detection, minify and one-click copy. 100% private.

No Tracking Runs in Browser Free
Output

What is JSON?

JSON (JavaScript Object Notation) is a lightweight, text-based data interchange format that is easy for humans to read and write, and easy for machines to parse and generate. Created by Douglas Crockford in the early 2000s and formalized as RFC 8259, JSON has become the universal standard for data exchange across virtually all programming languages, APIs, and web services.

JSON supports six data types: strings (in double quotes), numbers, booleans (true/false), null, arrays (ordered lists), and objects (key-value pairs). Its simplicity and readability have made it the preferred format over XML for most modern web applications, REST APIs, and configuration files.

A JSON formatter transforms raw or minified JSON into a well-structured, indented format that makes the data hierarchy immediately visible. This is essential for debugging API responses, inspecting configuration files, and understanding complex nested data structures. Unlike XML, JSON does not support comments, attributes, or namespaces — it focuses purely on data representation.

{
  "name": "Alice",
  "age": 30,
  "isActive": true,
  "skills": ["JavaScript", "Python"],
  "address": null
}

Key Features

Instant Formatting

Paste any JSON and get perfectly indented output in milliseconds. Supports 2-space and 4-space indentation.

Real-Time Validation

Automatically detects syntax errors as you type, with clear error messages pointing to the exact line and position.

One-Click Minify

Compress formatted JSON into a single line to reduce file size for production APIs and config files.

100% Browser-Based

All processing happens locally in your browser. Your data never leaves your device — no server uploads, no tracking.

Handles Large Files

Efficiently processes JSON files up to 10MB with smooth performance, no file size warnings or crashes.

Copy & Download

Export results instantly — copy to clipboard or download as a .json file with one click.

Examples

API Response

{"status":200,"data":{"user":{"id":"usr_2x7kP9","name":"Alice Chen","email":"alice@example.com","roles":["admin","editor"],"lastLogin":"2026-03-12T08:30:00Z"},"meta":{"requestId":"req_abc123","timestamp":1741776600}}}

Format a typical REST API response with nested user data and metadata

Package Config

{"name":"my-app","version":"2.1.0","private":true,"scripts":{"dev":"next dev","build":"next build","start":"next start","lint":"eslint ."},"dependencies":{"react":"^18.2.0","next":"14.1.0"},"devDependencies":{"typescript":"^5.3.0","eslint":"^8.56.0"}}

Beautify a minified package.json configuration file

Data Collection

[{"id":1,"product":"Laptop Pro","price":1299.99,"inStock":true,"tags":["electronics","computers"]},{"id":2,"product":"Wireless Mouse","price":29.99,"inStock":false,"tags":["electronics","accessories"]},{"id":3,"product":"USB-C Hub","price":49.99,"inStock":true,"tags":["electronics","accessories"]}]

Format an array of product objects from a database or e-commerce API

Nested Config

{"database":{"host":"localhost","port":5432,"name":"mydb","pool":{"min":2,"max":10}},"cache":{"enabled":true,"ttl":3600,"provider":"redis"},"logging":{"level":"info","format":"json","outputs":["stdout","file"]}}

Indent a deeply nested application configuration with database, cache, and logging settings

How to Use

  1. 1

    Paste Your JSON

    Enter or paste your raw JSON data into the input field above. You can also click 'Load example' to try a sample.

  2. 2

    Format or Minify

    Click 'Format JSON' to pretty-print with indentation, or 'Minify JSON' to compress into a single line.

  3. 3

    Copy the Result

    The processed result appears in the output area. Click 'Copy' to copy it to your clipboard instantly.

Common JSON Errors

Trailing Commas

JSON does not allow a comma after the last element in an array or object. This is one of the most common errors, especially when copying from JavaScript code.

✗ Wrong
{"name": "Alice", "age": 30,}
✓ Correct
{"name": "Alice", "age": 30}

Single Quotes

JSON requires double quotes for all strings and keys. Single quotes are valid in JavaScript but not in JSON.

✗ Wrong
{'name': 'Alice'}
✓ Correct
{"name": "Alice"}

Unquoted Keys

All property keys in JSON must be enclosed in double quotes. Unquoted keys are valid in JavaScript objects but not in JSON.

✗ Wrong
{name: "Alice"}
✓ Correct
{"name": "Alice"}

Comments

Standard JSON does not support comments of any kind. If you need comments, consider using JSONC (JSON with Comments) or YAML instead.

✗ Wrong
{"name": "Alice" // user name}
✓ Correct
{"name": "Alice"}

Missing Brackets

Every opening bracket or brace must have a matching closing bracket or brace. Mismatched brackets cause 'Unexpected end of JSON input' errors.

✗ Wrong
{"users": [{"name": "Alice"}
✓ Correct
{"users": [{"name": "Alice"}]}

Unexpected Token

This error occurs when the parser encounters a character that doesn't belong at that position. Common causes include missing commas between elements or extra characters after the JSON ends.

✗ Wrong
{"name": "Alice" "age": 30}
✓ Correct
{"name": "Alice", "age": 30}

Common Use Cases

API Response Debugging
Format minified API responses into readable JSON for quick debugging and inspection.
Configuration Files
Validate and beautify config files like package.json, tsconfig.json, and .eslintrc.
Data Inspection
Explore and understand JSON data exported from databases, logs, or third-party services.
Code Review
Format JSON snippets for clearer diffs and easier comparison during code reviews.
Documentation
Generate neatly formatted JSON examples for technical documentation and tutorials.
Data Migration
Validate JSON structure and syntax before importing data into new systems.

Technical Details

RFC 8259 Compliant
Full support for the standard JSON specification including Unicode and escaped characters.
Browser-Based Processing
All formatting runs locally in your browser using native JSON.parse() and JSON.stringify().
File Size Support
Handles JSON files up to 10MB with configurable indentation (2 or 4 spaces).

Best Practices

Validate Before Use
Always validate JSON data before using it in production to catch syntax errors early.
Use Consistent Indentation
Stick to 2-space indent for readability and smaller file sizes in version control.
Minify for Production
Use minified JSON in API responses and config files to reduce bandwidth and load time.

Frequently Asked Questions

How do I format JSON online?
Paste your raw or minified JSON into the input field above and click "Format JSON." The tool instantly parses your data, validates the syntax, and displays a properly indented version with 2-space indentation. You can then copy the result to your clipboard with one click. Everything runs locally in your browser — no data is sent to any server.
How do I validate JSON?
Paste your JSON into the input field and click "Format JSON." If the JSON contains syntax errors, the tool displays a detailed error message showing what went wrong and where. If the JSON is valid, it will be formatted and displayed in the output area. This tool validates against RFC 8259, the current JSON standard.
How do I minify JSON?
Paste your JSON into the input field and click "Minify JSON." The tool removes all unnecessary whitespace, line breaks, and indentation to produce the most compact representation. Minified JSON is ideal for API responses, configuration files in production, and anywhere file size or bandwidth matters.
Is my JSON data safe when using this tool?
Yes, completely. All processing happens locally in your browser using JavaScript's native JSON.parse() and JSON.stringify() — your data never leaves your device. There are no server uploads, no cookies, no analytics tracking on your input, and no data storage of any kind. This makes it safe to use with API keys, credentials, and proprietary data.
How do I fix "Unexpected token" errors in JSON?
An "Unexpected token" error means the JSON parser found a character that doesn't belong at that position. The most common causes are: a missing comma between elements ({"name": "Alice" "age": 30}), a trailing comma after the last element ({"name": "Alice",}), or extra characters after the JSON ends. Paste your JSON into this tool to see the exact error location, then check the characters around that position.
Why does my JSON have a "trailing comma" error?
JSON does not allow a comma after the last element in an object or array. This is one of the most common errors because JavaScript and many other languages permit trailing commas. For example, {"name": "Alice", "age": 30,} is invalid JSON — remove the comma after 30 to fix it. If you frequently copy data from JavaScript code, always check for trailing commas before using it as JSON.
Can I use single quotes in JSON?
No. JSON requires double quotes for all strings and property keys. Single quotes are valid in JavaScript and Python, but they are not part of the JSON specification (RFC 8259). For example, {'name': 'Alice'} is invalid — it must be {"name": "Alice"}. If you have data with single quotes, this tool will report a syntax error and show you the exact position to fix.
Can I add comments to JSON?
No, standard JSON does not support comments of any kind — no //, /* */, or # syntax. This was an intentional design decision to keep JSON simple and parseable. If you need comments in configuration files, consider JSONC (JSON with Comments, used by VS Code and TypeScript), JSON5, or YAML. To use commented files as standard JSON, strip the comments before parsing.
Why is my JSON not parsing correctly?
The most common reasons JSON fails to parse are: (1) trailing commas after the last element, (2) single quotes instead of double quotes, (3) unquoted property keys, (4) comments in the data, (5) missing or extra brackets/braces, (6) unescaped special characters like backslashes or newlines inside strings. Paste your JSON into this tool — it will pinpoint the exact error type and location so you can fix it quickly.
What is the difference between JSON and YAML?
Both JSON and YAML are data serialization formats, but they differ in design philosophy. JSON uses braces, brackets, and double quotes with a strict syntax — making it ideal for machine parsing and APIs. YAML uses indentation and minimal punctuation — making it more human-readable and popular for configuration files (Docker Compose, Kubernetes, GitHub Actions). JSON is a subset of YAML, so any valid JSON is also valid YAML, but not vice versa.
What is JSON Schema?
JSON Schema is a separate standard (not part of JSON itself) that defines the expected structure, types, and constraints of JSON data. For example, you can specify that a field must be a string, a number must be between 1 and 100, or an array must contain at least one element. JSON Schema is widely used for API request/response validation, form generation, and documentation. This tool validates JSON syntax, not JSON Schema — for schema validation, use a dedicated JSON Schema validator.
What is the difference between JSON and JSON5?
JSON5 is an extension of JSON that adds features developers frequently request: single and double quotes, trailing commas, comments (// and /* */), unquoted keys, multiline strings, and hexadecimal numbers. JSON5 is often used in configuration files where human editing is common. Standard JSON parsers cannot read JSON5 — you need a JSON5 parser. This tool works with standard JSON (RFC 8259) only.
What is the maximum size of a JSON file?
The JSON specification itself has no file size limit. Practical limits depend on the parser and environment: browsers typically handle JSON up to 500 MB–1 GB before running into memory issues, while server-side parsers (Node.js, Python, Java) can handle larger files with streaming parsers. This online tool efficiently handles JSON up to about 10 MB. For very large JSON files, consider using command-line tools like jq or streaming parsers.

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