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JSON Formatter & Validator — Free Online Tool
How to use
- Paste or type raw JSON into the Input panel
- Click Format to pretty-print with syntax highlighting
- Click Minify to compress into a single line
- Use the indent selector to switch between 2 spaces, 4 spaces, or tabs
- Click Copy to copy the output to your clipboard
- Errors display the exact line number and a hint to fix it
Features
- Pretty-print JSON with configurable indentation
- Minify JSON to a single line for production use
- Instant validation with descriptive error messages
- Syntax highlighting for keys, strings, numbers, and booleans
- Paste from clipboard in one click
- 100% client-side — nothing is sent to a server
- Works offline once the page is loaded
Frequently Asked Questions
Is my JSON data sent to a server?
No. All processing happens entirely in your browser using JavaScript. Your data never leaves your device.
What is the difference between formatting and minifying JSON?
Formatting (pretty-printing) adds indentation and line breaks to make JSON human-readable. Minifying removes all unnecessary whitespace to produce the smallest possible string, which is faster to transmit over a network.
Why does the validator say my JSON is invalid?
Common causes: trailing commas after the last element, unquoted keys, single quotes instead of double quotes, or JavaScript-style comments. JSON requires strict RFC 8259 syntax.
What's the maximum size JSON this tool can handle?
There is no server-side limit since processing is local. Very large files (10 MB+) may be slow depending on your browser and available memory.
Can I sort JSON keys alphabetically?
This tool formats and validates JSON. Key sorting is not currently a feature, but you can copy the output into a code editor that supports JSON sorting.
Does it support JSON5 or JSONL?
This tool validates strict RFC 8259 JSON. JSON5 (with comments, trailing commas) and JSONL (line-delimited JSON) are not supported in this version.