JSON Formatter & Validator

Beautify, format, and validate your JSON data instantly. Our free online tool helps you debug JSON by making it readable. 100% private and runs in your browser.

Format and validate JSON without uploading your data

Beautify, minify, and validate JSON instantly — right in your browser. No uploads, no sign-up, no limits.

100% private

Instant formatting

Free forever

How to use

1
Paste Your JSON
Copy and paste your raw, unformatted JSON data into the 'Input JSON' text area. You can also drag and drop a .json file.
2
Format and Validate
Click the 'Format / Validate' button. The tool will process the data instantly and display the result below.
3
Review the Output
If your JSON is valid, it will appear beautifully formatted with proper indentation. If there is an error, a detailed error message with line and column number will be displayed.
4
Copy or Download
Click 'Copy Result' to copy the formatted JSON to your clipboard, or use the Download button to save it as a .json file.

Powerful, Simple, and Secure

Everything you need to debug and format JSON, right in your browser.

Instant Formatting

Transform messy, single-line JSON into a neatly indented, human-readable format with a single click. Supports 2-space and 4-space indentation.

Error Highlighting

Quickly find syntax errors. Our validator points out exactly what's wrong and where, with line and column numbers, saving you valuable debugging time.

100% Private

Your data never leaves your machine. All processing happens locally in your browser, ensuring complete confidentiality for sensitive data.

Tree View

Collapse and expand nested objects and arrays visually. Perfect for navigating large, deeply nested API responses.

Minify Mode

Compress formatted JSON back to a single line to reduce payload size for network传输. One click to switch between pretty and minified.

Free with No Limits

No registration, no API key, no daily quotas. Free for personal and commercial use, forever.

Understanding JSON Formatting

What is JSON and why format it?

JSON (JavaScript Object Notation) is a lightweight data-interchange format that has become the de facto standard for APIs, configuration files, and data storage. It uses human-readable text to represent objects, arrays, numbers, strings, booleans, and null values. While JSON is designed to be easy for humans to read and write, many JSON payloads are transmitted in minified form (no whitespace) to save bandwidth, making them difficult to inspect.

A JSON formatter (also called a beautifier or pretty-printer) takes minified or poorly formatted JSON and adds consistent indentation, line breaks, and spacing so that the structure is immediately visible. For example, a single-line JSON string like `{"name":"John","address":{"city":"NYC","zip":"10001"}}` becomes a multi-line, indented structure where the nesting of objects and arrays is clear at a glance.

Common JSON errors and how to fix them

JSON has a strict syntax defined by RFC 8259. The most common errors are: using single quotes instead of double quotes for strings, trailing commas after the last element in an array or object, unquoted property names, and unescaped special characters in strings. Our validator detects all of these and reports the exact line and column where the error occurs.

Another common issue is mixing JSON with JavaScript. JSON is not JavaScript — it does not support comments (// or /* */), it does not support single-quoted strings, and it does not support trailing commas. If your JSON works in JavaScript but fails in a strict parser, it's likely because it contains one of these JavaScript-specific extensions.

Why Format JSON?

Common scenarios where a JSON formatter saves time and prevents errors.

Readability

Quickly grasp the structure of an API response or a configuration file. Indented JSON is 10x easier to read than a minified single line.

Debugging

Easily spot missing commas, mismatched brackets, or other common syntax errors that break your application.

Sharing

Share JSON data with colleagues in a clean, professional format that's easy to read in any text editor or code viewer.

Configuration Files

Format and validate configuration files (package.json, tsconfig.json, .eslintrc) before committing them to version control.

How does this compare to other JSON formatters?

A side-by-side comparison of popular JSON formatting tools.

Feature	NovaTools	JSONFormatter.org	JSONLint	VS Code
Privacy (no upload)	100% local	Uploads to server	Uploads to server	Local
Price	Free unlimited	Free with ads	Free with ads	Free
Registration required	No	No	No	N/A
Error highlighting	Line + column			On save
Tree view
Minify mode
Mobile friendly			Limited
Works offline	After page load

Online formatters like JSONFormatter.org and JSONLint upload your JSON to their servers. Our tool processes everything locally — your data never leaves your browser.

JSON Syntax Quick Reference

A quick guide to JSON data types and syntax rules.

Data Types

Symbol / Code	Description	Example
`string`	Text wrapped in double quotes. Single quotes are not valid.	`"hello world"`
`number`	Integer or floating point. No quotes needed.	`42 or 3.14`
`boolean`	true or false (lowercase, no quotes).	`true`
`null`	Represents absence of value (lowercase, no quotes).	`null`
`object`	Key-value pairs wrapped in curly braces.	`{"key": "value"}`
`array`	Ordered list wrapped in square brackets.	`[1, 2, 3]`

string

Text wrapped in double quotes. Single quotes are not valid.

Example:"hello world"

number

Integer or floating point. No quotes needed.

Example:42 or 3.14

boolean

true or false (lowercase, no quotes).

Example:true

null

Represents absence of value (lowercase, no quotes).

Example:null

object

Key-value pairs wrapped in curly braces.

Example:{"key": "value"}

array

Ordered list wrapped in square brackets.

Example:[1, 2, 3]

Common Syntax Rules

Symbol / Code	Description	Example
`"key":`	Property names must be wrapped in double quotes.	`"name": "John"`
`,`	Comma separates elements. No trailing comma allowed.	`[1, 2, 3] (not [1, 2, 3,])`
`\"`	Escape double quotes inside strings with backslash.	`"He said \"hi\""`
`\\`	Escape backslash itself with another backslash.	`"C:\\Users"`
`\n`	Newline character in strings.	`"Line1\nLine2"`

"key":

Property names must be wrapped in double quotes.

Example:"name": "John"

,

Comma separates elements. No trailing comma allowed.

Example:[1, 2, 3] (not [1, 2, 3,])

\"

Escape double quotes inside strings with backslash.

Example:"He said \"hi\""

\\

Escape backslash itself with another backslash.

Example:"C:\\Users"

\n

Newline character in strings.

Example:"Line1\nLine2"

FAQ

Is my data safe with this tool?

Yes, your data is 100% safe. This tool performs all formatting and validation directly in your browser using JavaScript. Your JSON data is never sent to our servers, never stored in any database, and never logged. You can verify this by opening your browser's DevTools Network tab — no network requests are made when you format JSON. This makes the tool safe to use with API keys, credentials, customer data, and other sensitive information embedded in your JSON.

What does 'validating' JSON mean?

Validation is the process of checking if your JSON data adheres to the correct syntax rules defined by RFC 8259. This includes checking for matching curly braces {}, matching square brackets [], correct quoting of strings with double quotes (not single quotes), proper comma placement between elements, and ensuring that numbers, booleans, and null values are written correctly. Our tool validates your JSON automatically as you paste it and highlights the exact location of any syntax error.

Can this tool handle large JSON files?

Yes. The tool is designed to handle large JSON files efficiently using a streaming parser. Since all processing is done on your local machine, performance depends on your computer's processing power and available memory. Files up to 5-10 MB typically format instantly. For files larger than 50 MB, you may notice a brief delay (1-3 seconds) while the parser processes the data. Very large files (100+ MB) may cause the browser tab to become temporarily unresponsive.

What is the difference between JSON and JSONL?

JSON (JavaScript Object Notation) is a single data structure — either an object or an array — that represents the entire document. JSONL (JSON Lines) is a format where each line is a separate, independent JSON object, commonly used for log files and data pipelines. Our formatter expects standard JSON, not JSONL. If you paste JSONL, the validator will report an error because multiple top-level JSON values are not valid in a single JSON document.

How do I fix 'Unexpected token' errors?

This error occurs when the JSON parser encounters a character it does not expect. The most common causes are: (1) using single quotes instead of double quotes for strings, (2) trailing commas after the last element in an array or object, (3) unquoted property names, (4) comments (JSON does not support comments — use JSON5 or JSONC if you need them), and (5) special characters in strings that are not properly escaped. Our tool highlights the exact character position of the error so you can find and fix it quickly.

Can I minify JSON with this tool?

Yes. After formatting, you can click the 'Minify' button to compress the JSON back to a single line with no whitespace. This is useful for reducing the size of JSON payloads sent over the network. Minified JSON is typically 20-40% smaller than pretty-printed JSON because it removes all unnecessary whitespace, newlines, and indentation. The minified output is still valid JSON and can be re-formatted at any time.

Does this tool support JSON with comments (JSONC)?

No. Standard JSON (RFC 8259) does not support comments. If your JSON contains comments (lines starting with // or blocks wrapped in /* */), the validator will report a syntax error. JSONC and JSON5 are extended formats that do support comments, but they are not standard JSON. If you need to add notes to your JSON, consider using a separate documentation file or a format like YAML that natively supports comments.

How is this different from VS Code's JSON formatter?

VS Code's built-in formatter works great for local files but requires opening an editor and creating a file. Our tool is instant — paste your JSON and it's formatted immediately in any browser, with no installation, no file creation, and no setup. Our tool also provides explicit validation error messages with line and column numbers, which VS Code only shows on save. Additionally, our tool works on mobile devices where VS Code is not available.

Can I use this tool for commercial projects?

Yes. The tool is free for both personal and commercial use with no watermarks, no attribution required, and no usage limits. You retain full ownership of your data. There is no registration, no API key, and no subscription. The tool is particularly useful for QA teams, API developers, and data analysts who need to quickly inspect and validate JSON payloads.

What does the 'tree view' show?

The tree view renders your JSON as an expandable, collapsible hierarchy, allowing you to navigate nested objects and arrays visually. This is especially useful for large, deeply nested JSON structures where the raw text is hard to scan. You can click the expand/collapse arrows to show or hide sections, and the tree view highlights the path to the currently selected node, making it easy to understand the structure of complex API responses.

Your Privacy is Our Priority

This tool runs entirely in your browser.

We do not upload, store, or analyze your data.
Everything you process stays on your device.
All formatting and validation is performed locally using JavaScript — no network requests are made when you paste or format JSON.
You can use this tool with API keys, credentials, customer data, and other sensitive information with complete confidence.

Even if your internet connection drops mid-formatting, your data remains safe on your device.

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