JSON Validator Online – Check JSON Syntax

Local processing

Check JSON syntax, locate errors, and review parser details without uploading the payload.

Checks standard JSON syntax locally in your browser.
Ready to check.Choose Run check to inspect this input.

JSON validation guide

How to validate JSON syntax

Paste JSON into the validator above to check whether it follows standard JSON syntax. A valid document gets a clear pass result, while invalid data includes an error message, line, column, and nearby context. Processing stays in your browser. This tool is free to use. No account or payment is required.

Last updated

What you can do here

  • JSON syntax validation
  • Error line and column details
  • Nearby error context
  • Actionable next-step recommendations
  • Manual run control
  • Browser-local processing

How to use

  1. Paste the JSON text you want to validate.
  2. Run the check and review the overall syntax status.
  3. Use the reported line, column, and context to correct invalid syntax.
  4. After syntax passes, use the formatter or schema validator when you need those separate tasks.

What JSON validation checks

A JSON validator parses the complete document and confirms that objects, arrays, strings, numbers, booleans, and null values use valid JSON grammar. The checker reports a pass only after the complete input can be parsed successfully.

Validation checks syntax rather than business rules. A payload can be valid JSON while still missing fields required by an API or application.

Common JSON validation errors

The most frequent problems are trailing commas, single-quoted strings, unquoted object keys, mismatched brackets, and quotation marks or line breaks that were not escaped inside a string.

  • Object keys and string values must use double quotes.
  • Objects and arrays cannot end with a trailing comma.
  • Comments, undefined, NaN, and Infinity are not valid JSON values.

Validate sensitive API payloads locally

VetaTool performs validation and error inspection in the browser. API responses, configuration files, and copied request bodies are not sent to a validation server.

Checks run only when you choose Run check, so editing the payload does not repeatedly parse it in the background.

JSON validation example

The input contains a trailing comma. Removing it produces standard JSON that passes syntax validation.

Invalid JSON

{
  "name": "Ada",
  "active": true,
}

Valid JSON

{
  "name": "Ada",
  "active": true
}

Common questions

Frequently asked questions

Does the JSON validator upload my data?

No. JSON parsing, validation, and error inspection run locally in your browser.

What is the difference between validation and formatting?

Validation checks whether the input follows JSON syntax. Formatting rewrites already valid JSON with consistent indentation and line breaks.

Are comments and trailing commas valid JSON?

No. Standard JSON does not allow comments or trailing commas, even though some JavaScript-oriented formats accept them.

Can the validator locate a syntax error?

Yes. When the parser exposes a position, VetaTool reports the line, column, absolute character, and nearby source context.

Recommended next steps

Debugging a specific JSON issue? Browse JSON troubleshooting.