JSON formatter & validator
Validate, format or minify JSON without rounding large numbers or changing string content. Copy the result or download a JSON file.
Free to use · No sign-up · Inputs stay in your browser
Make a payload readable
Edit the sample or paste your own JSON. Formatting changes whitespace outside strings; number text, key order and duplicate keys are preserved.
Validated output
Valid JSON syntax. Original number values and string escapes retained.
Up to 200,000 characters and 100 nesting levels. Syntax validation does not check a schema or decide whether a payload is safe for your application.
Practice checking a data contract
A payload contains {"enabled":"false"}. The formatter accepts it. Does that prove enabled is a Boolean?
Check the reasoning
No. "false" is a string. JSON syntax validation does not establish a field’s expected type. Read the consumer’s contract and test the boundary where the payload becomes application data.
This is an original open example, not a scored drill. Close the tool before taking a diagnostic or an unassisted practice session.
About 14 minutes, no account needed. A free account adds a daily practice queue; paid plans add more practice and the full library.
How to use the result
Paste JSON, choose 2-space or 4-space indentation, or select Minify. Invalid input clears the output. Limits are 200,000 input characters, 100 nesting levels and 1,000,000 output characters. Valid JSON syntax does not establish schema validity; duplicate keys are preserved, not resolved.
The sample ID 9007199254740993 stays exactly as written. The formatter validates syntax and changes only whitespace outside strings, preserving numeric literals, duplicate keys and key order.
These utilities and open examples do not contribute to your diagnostic score or practice history.
MDN: JSON and number precision