To validate JSON data online, follow these steps:

1. Choose a JSON validator: Use JsonViewer.tools, JSONLint, or similar online tools
2. Paste your data: Copy and paste your JSON content into the validator
3. Check results: The tool will immediately show validation results
4. Fix errors: If errors exist, they'll be highlighted with line numbers

Popular online JSON validators include:

• JsonViewer.tools - Fast validation with formatting
• JSONLint.com - Simple validator with error highlighting
• JSON Editor Online - Validation with editing capabilities

JSON becomes invalid due to several common syntax violations:

There are several methods to verify JSON format correctness:

1. Online Validators

The fastest method for checking JSON format:

• Copy your JSON data
• Paste into a validator like JsonViewer.tools
• Receive instant feedback with error locations

2. Browser Developer Tools

Use browser console for quick validation:

try {
    JSON.parse(yourJsonString);
    console.log("Valid JSON");
} catch (error) {
    console.log("Invalid JSON:", error.message);
}

3. Text Editors with JSON Support

• Visual Studio Code with JSON extensions
• Notepad++ with JSON Viewer plugin
• Sublime Text with JSON packages

Here are the most frequently encountered JSON errors:

The best JSON validation tool depends on your specific needs:

Several command-line tools can validate JSON:

Using jq (Most Popular)

# Validate a JSON file
jq . filename.json

# Validate JSON from stdin
echo '{"name": "test"}' | jq .

# Check if valid (exit code 0 = valid)
jq . filename.json > /dev/null && echo "Valid JSON" || echo "Invalid JSON"

Using Python

# One-liner validation
python -c "import json; json.load(open('file.json'))"

# With error handling
python -c "
import json, sys
try:
    with open('file.json') as f:
        json.load(f)
    print('Valid JSON')
except ValueError as e:
    print(f'Invalid JSON: {e}')
    sys.exit(1)
"

Using Node.js

# Validate JSON file
node -e "JSON.parse(require('fs').readFileSync('file.json', 'utf8'))"

"Invalid JSON format" means your data doesn't conform to the JSON specification. This error occurs when:

Specification Violations

• Non-conforming syntax: Data doesn't follow JSON grammar rules
• Encoding issues: Non-UTF-8 characters or BOM markers
• Structural problems: Malformed objects or arrays

Common Scenarios

Error Resolution Steps

1. Use a JSON validator to identify specific errors
2. Check for common syntax mistakes
3. Ensure proper escaping of special characters
4. Verify data type compliance

JSON Schema validation goes beyond syntax checking to validate data structure and types:

What is JSON Schema?

JSON Schema is a vocabulary for validating the structure of JSON data. It defines:

• Required and optional properties
• Data types and formats
• Value constraints and patterns
• Array and object structures

Schema Validation Tools

• Online: JSON Schema Validator websites
• JavaScript: Ajv library (fastest JSON Schema validator)
• Python: jsonschema library
• Java: everit-org/json-schema

Example Schema Validation

{
  "$schema": "http://json-schema.org/draft-07/schema#",
  "type": "object",
  "properties": {
    "name": {
      "type": "string",
      "minLength": 1
    },
    "age": {
      "type": "integer",
      "minimum": 0,
      "maximum": 150
    },
    "email": {
      "type": "string",
      "format": "email"
    }
  },
  "required": ["name", "email"]
}

API response validation ensures data integrity in web applications:

Testing Approaches

Popular Testing Tools

• Postman: Built-in JSON validation and schema testing
• REST Assured: Java library for API testing
• Jest/Mocha: JavaScript testing frameworks
• pytest: Python testing with JSON validation