JSON Formatter, Validator & Prettifier
Format, validate, prettify, and minify complex JSON payloads. Catch syntax errors with exact line diagnostics. 100% free & private.
Mastering JSON Data: Formatting, Validation & Optimization
JavaScript Object Notation (JSON) is the universal lightweight data-interchange format used by web APIs, microservices, mobile applications, and configuration files (such as package.json and tsconfig.json). Reading unindented or minified JSON strings during debugging is difficult and prone to missing syntax errors.
How to Use
- Paste JSON Payload: Insert raw JSON string into the left input window.
- Instant Formatting: Prettify with 2 or 4 space indentation for readability.
- Minify for Production: Strip all whitespace to reduce payload bandwidth.
- Error Detection: Spot missing quotes, bracket mismatches, or trailing commas instantly.
100% Client-Side Privacy
Your API tokens, database records, and proprietary JSON payloads are processed 100% inside your browser. No data ever leaves your computer or passes through external cloud APIs.
Common JSON Syntax Rules & Pitfalls
1. Double Quotes Required
All object keys and string values must be enclosed in double quotes ("key": "value"), never single quotes.
2. No Trailing Commas
Strict JSON prohibits commas after the last item in an array or key in an object (e.g. {"a":1,} is invalid).
3. Supported Primitive Data Types
JSON supports String, Number, Boolean (true/false), Array ([]), Object ({}), and null.
4. Reserved Word Limitations
JSON does not support functions, undefined values, comments (// or /* */), or date objects directly.
Frequently Asked Questions
What is the difference between JSON Prettifying and Minifying?
Prettifying adds line breaks and indentation spaces to make JSON human-readable during development. Minifying removes all unneeded spaces and newlines to shrink payload file size for high-speed network transmission.
How does JSON validation error reporting work?
When invalid JSON is pasted into the tool, native JSON.parse() catches syntax exceptions and extracts the position marker, highlighting the exact character or line error in an alert banner.