Free JSON Formatter & Validator that works offline
Format and validate JSON without pasting API responses into a remote service. Choose two spaces, four spaces, tabs or minified output, and optionally sort object keys recursively for consistent comparison.
What this json formatter & validator does
Valid JSON follows strict rules: property names require double quotes, trailing commas are not allowed and values must use supported types. The formatter parses the complete input before producing output, so a successful result also confirms syntactic validity. Error messages include line and column details when the browser provides a position.
How to use the JSON Formatter & Validator
- Paste a JSON object, array or primitive into the input editor.
- Choose indentation and decide whether object keys should be sorted.
- Select Format & validate.
- Fix any reported syntax location or copy the formatted output.
Common uses
- Reading compact API responses and webhook payloads
- Minifying JSON configuration for transport
- Sorting keys before comparing two structures
- Checking generated JSON while keeping production samples local
Private processing and offline access
This tool does not submit your input to a conversion server. Processing takes place inside the browser using local JavaScript and standard Web APIs. After the PWA has been installed or cached, the page and its core features remain available without an internet connection. Closing or clearing the page removes unsaved input; the tool does not create an account or cloud history.
Tips for accurate results
- JSON is not JavaScript: comments, undefined and single-quoted keys are invalid.
- Sorting keys changes object presentation but leaves array order untouched.
- Avoid pasting secrets into any third-party site; this tool performs parsing only in your browser.
Frequently asked questions
Does formatting change JSON data?
Whitespace and optional object-key order may change, but parsed values and array order remain the same.
Can the tool repair invalid JSON automatically?
No. It reports the syntax error so you can make an intentional correction.
Is a top-level array valid JSON?
Yes. Objects, arrays, strings, numbers, booleans and null can all be valid top-level JSON values.