Three straightforward steps
- Choose or paste the input requested by this tool.
- Configure the options and run the operation locally.
- Review and download or copy the result.
Developer TOOL
JSON Formatter & Validator
Validate and pretty-print JSON with readable error messages.
ON-DEVICESelected input is processed in this browser.
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The selected input stays under your control
On-device processing means the input is handled by browser APIs on the device running this page. Closing or refreshing the page normally clears the active in-memory working session.
Read the Privacy Policy →Find JSON syntax problems faster
The formatter validates JSON before applying indentation. If parsing fails, inspect commas, quotation marks, brackets, and trailing characters near the reported location.
Formatting changes whitespace only. It does not verify that property names or values satisfy an external API schema.
What JSON formatting validates
The formatter first parses the input as JSON. Successful formatting confirms valid JSON syntax, but it does not confirm that the data follows a particular API contract or schema.
Fix common JSON errors
Check for missing commas, unquoted property names, single quotes, trailing commas, mismatched braces, and unexpected characters after the final value. JSON strings and property names require double quotes.
Formatting versus validation
Indentation makes nested data easier to inspect. For rules such as required properties, allowed values, or numeric ranges, use a schema-aware validator after the syntax is valid.
Questions about this tool
Does formatting change data values?
Formatting changes whitespace and indentation. Parsed property values remain the same, although insignificant source spacing is replaced.
Why is JavaScript object syntax rejected?
JSON is stricter than JavaScript object notation. Comments, functions, undefined values, single-quoted strings, and trailing commas are not valid JSON.
Validate JSON syntax and make nesting readable
Parse strict JSON, explain syntax failures and apply consistent indentation.
How to use it
- Paste JSON into the editor.
- Run validation. If it is invalid, use the reported line, column, highlighted source line and suggested correction.
- Correct the source, then copy or download the formatted result.
Supported input
- Objects and arrays in valid JSON
- Unicode JSON text
Worked example
Format a compact API response to inspect nested customer and order properties during debugging.
Limitations
- Syntax validity does not prove schema validity.
- Comments, single-quoted strings, unquoted property names and trailing commas are not part of strict JSON.
Troubleshooting
- Read the plain-language reason and How to fix guidance before using the technical parser details.
- Check the marked line for missing double quotes, commas or closing brackets.
- Remove JavaScript-only values such as undefined, NaN and Infinity.
Tool-specific questions
Does formatting change values?
Only insignificant whitespace is changed.
Why are single quotes rejected?
JSON strings and property names require double quotes.
How do I locate the error?
The error card reports a line and column, displays the affected source line and places a caret near the detected problem.
Before you process
Can I use this json formatter & validator online without uploading my input?
Yes. This tool is labelled On-device, so the selected input is processed in your browser and is not sent to a ForgeMyFile processing API.
What happens if the browser cannot process it?
The tool shows a readable error and stops. It does not silently fall back to a cloud upload.
Why can performance differ between devices?
The browser is doing the work locally, so speed and practical file size depend on available memory, CPU and browser capabilities.