JSON Formatter & Validator
Format, validate, and prettify JSON instantly.
How it works
- 1
Paste your JSON
Paste raw or minified JSON into the input area.
- 2
Click Format
Click the Format button to prettify the JSON with proper indentation.
- 3
Copy the result
Copy the formatted output or download it as a file.
Common use cases
Minified API response
{"name":"John","age":30,"city":"Johannesburg"}
Nested object
{"user":{"id":1,"roles":["admin","editor"]}}
About This Tool
Paste raw or minified JSON and instantly format it with proper indentation. This tool validates your JSON syntax in real time, highlights errors with the exact line and position, and lets you switch between 2-space and 4-space indentation.
Common use cases: formatting a minified API response to find a specific field, validating a config file before committing, cleaning up JSON copied from a database query, and checking whether a string is valid JSON before parsing it in code.
The formatter uses your browser's native JSON.parse() for validation -- the same engine your JavaScript code uses -- so the results are authoritative. If JSON.parse() accepts it, it is valid JSON. If it rejects it, the tool shows you exactly where the error is.
All processing runs entirely in your browser -- nothing is sent to any server. Your API responses, config files, and data structures stay on your device.
JSON (JavaScript Object Notation) is the de facto standard for data exchange in modern web development. REST APIs return JSON, configuration files like tsconfig.json and package.json use JSON, and databases like MongoDB store documents in a JSON-like format called BSON. Despite its simplicity, JSON can be difficult to read when minified -- a single line with no spaces or line breaks -- which is how most APIs deliver it to save bandwidth.
This formatter solves that problem by parsing the minified JSON and reconstructing it with consistent indentation and line breaks. It uses JSON.parse() under the hood, which means it validates against the exact same rules your JavaScript runtime uses. When validation fails, the tool catches the SyntaxError and extracts the error message, which typically includes the character position where parsing stopped. It then maps that position back to a line and column number so you can jump straight to the problem.
Real-world scenarios where this tool saves time: debugging a webhook payload that your server rejected, inspecting the response from a GraphQL query, verifying that a manually edited JSON config file is still syntactically correct, and transforming a one-liner from a curl response into something you can actually read. If you have ever pasted JSON into a file and run prettier or jq on it, this tool does the same thing without leaving your browser.
Tips and best practices: always validate JSON before committing it to version control, use 2-space indentation to match JavaScript conventions (4-space is fine for personal preference), and watch for trailing commas -- they are valid in JavaScript objects but not in JSON. If you copy JSON from a log file, look out for surrounding quotes that make it a JSON string rather than raw JSON.
More examples
Examples
Minified API response
Input
{"name":"John","age":30,"city":"Johannesburg"}Output
{
"name": "John",
"age": 30,
"city": "Johannesburg"
}Nested object
Input
{"user":{"id":1,"roles":["admin","editor"]}}Output
{
"user": {
"id": 1,
"roles": [
"admin",
"editor"
]
}
}Frequently Asked Questions
- What is JSON?
- JSON (JavaScript Object Notation) is a lightweight data interchange format that is easy for humans to read and write, and easy for machines to parse and generate.
- Is my data sent to a server?
- No. All formatting and validation happens entirely in your browser. Your data never leaves your device.
- Can this tool fix invalid JSON?
- This tool identifies and highlights JSON syntax errors so you can fix them manually. It shows the exact line and position of each error.
- What is the difference between a JSON formatter and a JSON validator?
- A JSON formatter (also called a JSON beautifier or pretty-printer) adds indentation and line breaks to make JSON readable. A JSON validator checks whether the JSON is syntactically correct. This tool does both: it validates first, then formats if valid, or shows the error location if invalid.
- How do I validate JSON online?
- Paste your JSON into the input area. The tool validates it in real time using JSON.parse(). If the JSON is valid, it formats it with proper indentation. If it is invalid, it highlights the error and shows the line number and position of the syntax problem.
- What are common JSON syntax errors?
- The most common errors are: trailing commas after the last item in an array or object (not allowed in JSON, unlike JavaScript), single quotes instead of double quotes for strings, unquoted property names, missing commas between items, and unclosed brackets or braces. The formatter highlights the exact location of each error.
- Does this tool support JSON with comments?
- Standard JSON does not support comments. If your input contains // or /* */ comments, JSON.parse() will reject it. JSONC (JSON with Comments) used in files like tsconfig.json is a separate format. This tool validates strict JSON per RFC 8259.
- Can I format large JSON files?
- Yes. The formatter handles files up to several megabytes. Very large files (10 MB+) may cause the browser to pause briefly during parsing. For extremely large files, command-line tools like jq or python -m json.tool may be more suitable.