JSON Formatter & Validator
Format, validate, and minify JSON data with syntax highlighting. RFC 8259 compliant parser. Processing happens locally in your browser.
Formatting and validation run locally, so a malformed document never leaves your machine. Validation reports the byte offset of the first syntax error, which is where JSON.parse stops.
Tool workspace
Format
Formats JSON with proper indentation (2 spaces) for readability.
Minify
Removes all whitespace to reduce file size for transmission.
Validate
Validates JSON against RFC 8259 specification.
Your JSON data is processed locally in your browser. No data is sent to any server.
How to Format and Validate JSON Online
Learn how to format, validate, and minify JSON data using a zero-knowledge, client-side tool.
- 1
Paste your JSON
Enter or paste your JSON data in the input box.
- 2
Choose an action
Select Format, Minify, or Validate based on your needs.
- 3
View results
See formatted JSON, validation errors, or minified output instantly.
- 4
Copy or compare
Copy the result to clipboard or compare two JSON documents.
Common Use Cases
- 1Pretty-print minified API responses for faster debugging
- 2Validate JSON before sending it to a backend or storing it
- 3Inspect configuration files and generated payloads during development
- 4Check machine-generated JSON for structural errors
Frequently Asked Questions
Is my JSON data uploaded?
No. Formatting, validation, and minification all happen locally in your browser.
What can the JSON tool do?
Format, minify, and validate JSON against RFC 8259, with error position reporting and document statistics.
Can it handle large documents?
Yes, but very large documents depend on your browser's memory and performance.
Why does the validator flag duplicate keys and unsafe key names?
Duplicate keys and keys such as __proto__, constructor, or prototype are legal JavaScript but risky in configuration and parsed objects, so the validator reports each location instead of silently keeping the last value. You can repair the document with the exact path in hand.
Is the formatted output safe to paste into code?
Formatting changes whitespace only, so values keep their original precision and ordering. Review any diagnostics first: a document that validates as JSON can still contain duplicate keys or numbers that lost precision.
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You are responsible for key management and output validation.