JSON Formatter & Validator
Format, validate, and minify JSON instantly in your browser
No data is sent to any server — everything runs client-side
JSON Input
Paste your JSON here
Result
Formatted or minified output
What Is JSON Formatting?
JSON formatting (also called “pretty-printing”) adds consistent indentation and line breaks to a JSON document to make it human-readable. Minified JSON removes all unnecessary whitespace to reduce file size for transmission and storage. Both operations preserve the data structure and values — only whitespace changes.
Pretty-printed JSON is essential for debugging API responses, reviewing configuration files, and sharing data structures with team members. Minified JSON is used in production APIs, stored payloads, and anywhere bandwidth matters. The difference can be significant: a 100 KB pretty-printed JSON document might compress to 60 KB when minified.
JSON Validation: Common Errors
The validator checks whether your input is syntactically valid JSON according to the ECMA-404 / RFC 8259 specification. Here are the most common errors developers encounter:
Trailing comma
JSON does not allow a comma after the last item in an object or array. Remove the trailing comma.
Single quotes
JSON requires double quotes for strings and keys. Single quotes are valid in JavaScript but not in JSON.
Unquoted keys
Every key must be a double-quoted string. Unquoted keys like {name: "value"} are invalid.
Comments
JSON does not support comments. If you need comments, consider JSONC (JSON with Comments) or YAML.
NaN, Infinity, undefined
These JavaScript values are not valid in JSON. Use null for missing values.
When to Use This Tool
Debugging API Responses
Paste a minified JSON response from an API call to see the full structure with proper indentation. This makes it easy to navigate deeply nested objects and find missing or unexpected fields.
Validating Config Files
Check package.json, tsconfig.json, or other JSON configs for syntax errors before committing. A misplaced comma or unquoted key can break builds silently.
Preparing Production Payloads
Minify JSON data before embedding in HTML, storing in databases, or sending over the wire. Smaller payloads mean faster APIs and lower bandwidth costs.
Sharing & Documentation
Format JSON examples for documentation, Slack messages, or issue reports. Well-formatted JSON is easier for reviewers and collaborators to understand.
JSON Data Types Quick Reference
| Type | Example | Notes |
|---|---|---|
| String | "hello world" | Must use double quotes |
| Number | 42, 3.14, -17, 2.998e8 | No NaN/Infinity, no leading zeros |
| Boolean | true, false | Lowercase only |
| Null | null | Lowercase only, represents absence of value |
| Object | {"key": "value"} | Unordered key-value pairs |
| Array | [1, "two", true] | Ordered list, can mix types |
Related Tools & Guides
How to Use the JSON Formatter & Validator
Paste your JSON
Copy a JSON string from an API response, config file, or any source and paste it into the input textarea.
Choose an action
Click "Format" to pretty-print with 2-space indentation, "Minify" to remove all whitespace, or "Validate" to check syntax without changing the output.
Review the output
The formatted or minified JSON appears in the output panel. Syntax errors are highlighted with a clear error message showing what went wrong.
Copy or use the result
Click Copy to copy the output to your clipboard for use in your code, documentation, or API client.
Frequently Asked Questions
What is the difference between Format and Minify?▼
Format (pretty-print) adds consistent 2-space indentation and newlines to make JSON human-readable. Minify removes all unnecessary whitespace, producing the most compact representation for production use in APIs and storage.
Why does JSON not allow trailing commas?▼
The JSON specification (ECMA-404, RFC 8259) does not allow trailing commas after the last object property or array element. This was a deliberate design decision to keep JSON parsing simple. If you need trailing commas, consider JSONC or YAML.
Can I validate JSON Schema here?▼
This tool validates JSON syntax (well-formedness), not JSON Schema conformance. For Schema validation, you need a dedicated JSON Schema validator. Once your JSON is syntactically valid, you can use it with offline validators.
My JSON has comments and fails to validate. What should I do?▼
Standard JSON does not support comments. If your source has // or /* */ comments (a format called JSONC), remove them before validating. Many editors (VS Code, IntelliJ) can strip comments. Alternatively, convert to YAML which does support comments.
Is my data sent to a server?▼
No. All formatting and validation happens entirely in your browser using JavaScripts native JSON.parse() and JSON.stringify(). Your data never leaves your device.
Further Reading
Go deeper on JSON with our developer guides.
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