Validate JSON Online — Free JSON Syntax Checker

How to Validate JSON Online

JSON validation checks whether your data conforms to the JSON specification (ECMA-404). A valid JSON document must have properly quoted keys, matching brackets, correct comma placement, and valid value types (string, number, boolean, null, array, object). Even a single missing comma or unquoted key will make the entire document invalid.

Paste your JSON into the tool above and click submit. The validator will either confirm your JSON is valid or pinpoint the exact location of the first error — including line number and character position — so you can fix it immediately.

Common JSON Validation Errors

Validate JSON Programmatically

// JavaScript
try {
    const data = JSON.parse(jsonString);
    console.log('Valid JSON');
} catch (e) {
    console.error('Invalid:', e.message);
}

# Python
import json
try:
    data = json.loads(json_string)
    print('Valid JSON')
except json.JSONDecodeError as e:
    print(f'Invalid: {e.msg} at line {e.lineno} col {e.colno}')

JSON Validation Best Practices

• Validate before parsing: Always validate incoming JSON from APIs, webhooks, and user input before processing it in your application.
• Use schema validation: For complex data structures, combine syntax validation with JSON Schema to enforce required fields, types, and value constraints.
• Check encoding: JSON must be UTF-8 encoded. BOM characters or other encodings will cause validation failures.
• Watch for truncation: Incomplete JSON from network timeouts or buffer limits is a common source of validation errors in production.