What makes JSON invalid?

Common JSON errors: missing quotes around keys, trailing commas, single quotes instead of double quotes, unescaped special characters, mismatched brackets, or using undefined/NaN values. The validator shows exactly where errors occur.

How does the validator find errors?

The validator parses your JSON character by character following strict syntax rules. When it finds an issue, it highlights the problematic line and shows the error type: syntax error, unexpected token, or structural problem.

Can I validate large JSON files?

Yes, the validator handles large JSON files efficiently. However, extremely large files (over 1MB) might slow down in the browser. For production use, consider command-line validators or streaming parsers for very large data.

JSON Validator - Validate JSON

Input JSONPaste your JSON here

Parsed Preview

Parsed result will appear here...

What is JSON Validator?

JSON validation is the process of checking whether a JSON string conforms to the correct syntax and structure defined by the JSON specification. This tool analyzes your JSON input character by character to identify syntax errors, structural issues, and potential problems that could cause your application to fail when parsing the data.

How to Use

Paste your JSON data into the input field on the left side.
Click the 'Validate JSON' button to analyze your input.
Review the validation result - valid JSON will show a green success message.
If errors are found, check the error details including line and column numbers.
Use the 'Load Invalid Sample' button to see how error detection works.
Fix the identified issues in your JSON and re-validate until successful.

Why Use This Tool?

Pinpoint exact error locations with line and column numbers

Detect duplicate keys in objects that could cause data issues

Instant validation without sending data to external servers

Clear error messages that explain what went wrong

Parsed preview shows how valid JSON should look when formatted

Learn JSON syntax by testing valid and invalid samples

Tips & Best Practices

Always validate JSON before using it in production code
Use the parsed preview to understand correct JSON structure
Check for duplicate keys - they can cause unexpected behavior in some parsers
Common errors include missing quotes, trailing commas, and incorrect escape sequences
Copy the parsed preview directly into your code editor after validation

Frequently Asked Questions

What types of errors can this validator detect?

This validator detects all standard JSON syntax errors including: missing or mismatched quotes, invalid escape sequences, trailing commas, missing commas between elements, incorrect data types, malformed arrays and objects, and duplicate keys in objects. Each error is reported with its location for easy debugging.

Why does my JSON show 'duplicate key' warnings?

Duplicate keys in JSON objects are technically allowed by the JSON specification but can cause serious problems. Different JSON parsers handle them differently - some keep the last value, some keep the first, and some throw errors. This warning helps you avoid unexpected behavior in your applications.

How accurate are the line and column numbers?

The validator calculates line and column numbers based on the character position where the error occurred. For syntax errors like unexpected characters, the location is precise. For structural errors like missing brackets, it shows where the parser detected the problem.

Can I validate JSON from API responses?

Yes, this tool is perfect for validating API responses. Copy the response body from your API call, paste it into the validator, and quickly identify any syntax issues. This is especially useful during API integration and debugging.

What's the difference between errors and warnings?

Errors are critical issues that make your JSON invalid and cannot be parsed. Warnings are potential problems like duplicate keys that won't prevent parsing but may cause unexpected behavior in your application. Both should be addressed for reliable JSON data.

Is my validated JSON secure?

Absolutely. All validation happens in your browser using JavaScript. Your JSON data is never sent to any server, never stored, and never logged. Once you close the page, all your input is gone. This makes it safe to validate sensitive data like API keys or credentials.

JSON Validator