JSON Formatter & Validator
Format JSON or check its syntax without rounding large numbers during formatting. Validation does not verify an application’s data schema.
Validation checks JSON syntax, not required fields or a schema. Fix the reported error and validate again.
Practical guides
Reproducible examples that explain a tool's result, not just its buttons.
What is JSON Formatter & Validator?
Formatting changes whitespace outside string values, not the data tokens. Apps24 first checks JSON syntax, then indents the original tokens instead of serializing parsed JavaScript numbers. This preserves numeric spelling, property order and duplicate property names in the formatted text.
When to use this tool?
Use it to inspect API responses and configuration files. Syntax success only means the text is valid JSON: it does not prove that a URL works, a field is required, a value is safe or a business rule is satisfied.
Examples
- Invalid: {"name":"Apps24",}. Remove the trailing comma: {"name":"Apps24"}.
- The integer 9007199254740993 remains unchanged when formatted; converting it to a JavaScript Number elsewhere may lose precision.
How to use JSON Formatter & Validator
1. Paste JSON or load the sample. 2. Choose validation to check syntax, or formatting to add indentation. 3. Read the success or error message. Correct syntax errors manually; the tool does not guess missing values.
Quick Setups
References
Frequently Asked Questions
Q: Are duplicate property names safe?
A: The formatter preserves them, but consumers may keep only the last value or reject them. Use unique names for interoperable data.
Q: Are comments and single-quoted strings accepted?
A: No. Standard JSON uses double-quoted names and strings and does not allow comments or trailing commas. JSON5 is a different format.
How it works
Parsing checks syntax locally. Token-based formatting preserves source values, while schema and domain validation remain the responsibility of the receiving application.