JSON Formatter and Validator
Validate, pretty-print with custom indentation, or minify JSON data while pinpointing syntax errors.
What does the JSON Formatter do and how to use it?
The Herramix JSON Formatter & Validator turns minified or messy JSON payloads into clean, human-readable trees (pretty print) or compresses formatted JSON into a single compact line (minify). At the same time, it verifies strict compliance with the RFC 8259 JSON specification.
When your JSON contains a syntax mistake—such as a trailing comma, unquoted key, or missing bracket—the validator highlights the error message along with the approximate line and column number so you can fix it immediately.
You can also click Sort keys to recursively order all object keys alphabetically, making it easy to diff two configuration files or API responses.
Usage example
Minified JSON input: {"server":"api.example.com","port":443,"tls":true}
Output after clicking "Format / Validate": Valid JSON indented across 5 lines with 2-space indentation, ready to inspect or copy.
Frequently Asked Questions
Is it safe to paste private API responses or sensitive JSON here?
Yes, 100% safe. Parsing and formatting run exclusively inside your browser's memory via native JSON.parse and JSON.stringify. None of your data is sent over the network.
Why is my JSON failing validation?
The most common issues are using single quotes ('key') instead of required double quotes ("key"), leaving a trailing comma after the last item in an object or array, or including comments (//).
What is the difference between formatting and minifying JSON?
Formatting (pretty-printing) inserts line breaks and indentation so developers can read nested structures easily. Minifying removes all non-essential whitespace to reduce byte size for network transfer.