What is JSON Formatting and Validation?
JavaScript Object Notation (JSON) is the universal data interchange format powering modern web APIs, microservices, configuration files, and databases. Because APIs often compress JSON into minified single-line payloads to save bandwidth, debugging raw responses manually is difficult and prone to oversight.
A JSON formatter parses raw strings, validates strict JSON syntax rules, and formats data into clear, hierarchically indented structures with syntax highlighting. It pinpoints line-specific syntax errors like missing commas, unescaped quotes, or trailing commas so you can fix issues immediately.
How to Use This JSON Formatter (3-Step Quick Guide)
Paste Raw JSON
Paste raw, unformatted, or minified JSON text into the editor.
Validate & Format
Click Beautify or Minify to format the data and verify complete syntactic correctness.
Copy or Download
Copy the indented result to your clipboard or download it as a clean .json file.
JSON Data Types & Syntax Rules
Core structural specifications of RFC 8259 JSON format.
| Data Type | Valid Syntax | Common Mistake to Avoid |
|---|---|---|
| String | "hello world" | Single quotes `'hello'` are invalid in JSON |
| Number | 42 or 3.14 | Leading zeros or octal notation are invalid |
| Boolean | true or false | Must be lowercase (not True or FALSE) |
| Null | null | Must be lowercase (not None or NULL) |
| Array | [1, 2, "three"] | Trailing comma after last item is forbidden |
| Object | {"key": "value"} | Keys must always be wrapped in double quotes |
Frequently Asked Questions
Why does my JSON fail validation with single quotes?
The official JSON standard (RFC 8259) strictly requires double quotes for all keys and string values. Single quotes are invalid JSON syntax.
Are trailing commas allowed in JSON?
No. Unlike JavaScript object literals, standard JSON does not allow trailing commas after the final key or array item.
Is my JSON data sent to a server?
No. UniTools validates and formats all JSON locally inside your browser memory with zero external requests.