Free JSON Validator Online — Check Syntax Instantly

Invalid JSON breaks production APIs, CI pipelines, config files, and mobile app builds. A single trailing comma or unquoted key can cause hours of debugging. ToolsBaba JSON Validator checks your JSON syntax instantly — paste text or upload a file, get clear validation results, and fix errors before they ship.

Everything runs locally in your browser. Your API keys, config secrets, and customer data never leave your device.

What makes JSON invalid?

• Trailing commas after the last item in an array or object
• Single quotes instead of double quotes for strings
• Unescaped special characters inside strings
• Missing closing brackets ] or braces }
• Comments — standard JSON does not support // or /* */
• Undefined, NaN, or functions — not valid JSON values

How to validate JSON online

• Open ToolsBaba JSON Validator
• Paste your JSON into the editor or upload a .json file
• Click Validate — results appear instantly
• Fix any syntax errors reported
• Use JSON Formatter to pretty-print valid JSON for readability

Common use cases

• API request/response bodies before sending to production
• package.json, tsconfig.json, and CI config files
• Firebase, AWS, and Kubernetes JSON configs
• Webhook payloads and GraphQL variables
• Debugging mobile app JSON exports

JSON Validator vs JSON Formatter

The validator answers one question: is this JSON syntactically correct? The formatter beautifies already-valid JSON with indentation and line breaks. Run validate first, then format for sharing or code review.

Privacy

Unlike server-based validators, ToolsBaba processes JSON entirely on your machine. No upload, no logging, no account. Safe for proprietary configs and production API responses.