π Statistics & Probability
JSON Formatter & Validator
Format, validate, and beautify JSON instantly. Free JSON formatter with error highlighting.
What This Calculator Tells You
Paste JSON and this tool tells you immediately whether it is valid, then pretty-prints it with the indentation you choose. If it is invalid, you see the parser's error message so you can find the broken comma or quote.
Formatting happens entirely in your browser, so it is safe to use with API responses and config files.
What to Enter
- Paste JSON β an object, array or any JSON value.
- Indent spaces β 2 is the common default for web projects; 4 is popular in Python teams.
Worked Examples
1. A minified API response
A one-line response from a REST API.
- Formatted with 2 spaces, nested objects and arrays become readable in seconds.
2. A config file that will not load
The error points to an unexpected token near the end of the file.
- The usual cause is a trailing comma after the last item β accepted in JavaScript, invalid in JSON.
3. Checking a webhook payload
You copy the body from your logs before writing parsing code.
- Validating it first confirms the problem is in your code, not in malformed data.
How to Read Your Result
- β Valid JSON means it parses under the JSON standard (RFC 8259).
- β Invalid JSON shows the browser's parser message; the position it reports is where parsing failed, which can be just after the real mistake.
- Valid JSON can still be the wrong shape for your API β check field names and types too.
Common Mistakes to Avoid
- Single quotes β JSON requires double quotes around strings and keys.
- Trailing commas after the last element.
- Comments β standard JSON does not allow them.
- Unquoted keys, as in JavaScript object literals.
When to Use This Calculator
- Read and debug API responses.
- Validate config and data files before deploying.
- Inspect webhook payloads.
- Learn or teach JSON syntax.
Frequently Asked Questions
Is my JSON sent anywhere?
No. Validation and formatting run in your browser.
Why is my JSON invalid when it works in JavaScript?
JavaScript object syntax is more relaxed. JSON forbids single quotes, comments, trailing commas and unquoted keys.
Can it convert CSV to JSON?
Use the CSV to JSON converter for that.
What indentation should I use?
Match your project's style guide; 2 spaces is the most common.
Do you store the values I enter?
No. All calculations happen in your browser. Your data never leaves your device.
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