JSON Validation Guide - How to Validate JSON Data

1. Basic JSON Validation

Syntax Validation

Basic JSON syntax validation checks for:

Proper opening and closing brackets
Valid key-value pairs
Correct use of commas and colons
Proper string escaping

Example Valid JSON

{
    "name": "John Doe",
    "age": 30,
    "isStudent": false
}

Example Invalid JSON

{
    "name": "John Doe",
    "age": 30,
    "isStudent": false,  // Trailing comma
}

2. JSON Schema Validation

Schema Example

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

Validating Against Schema

const Ajv = require('ajv');
const ajv = new Ajv();

const schema = {
    // ... schema definition
};

const validate = ajv.compile(schema);
const valid = validate(data);

if (!valid) {
    console.log(validate.errors);
}

3. Common Validation Scenarios

Type Validation

{
    "type": "object",
    "properties": {
        "name": { "type": "string" },
        "age": { "type": "number" },
        "isActive": { "type": "boolean" },
        "tags": { "type": "array" }
    }
}

Format Validation

{
    "type": "object",
    "properties": {
        "email": { "format": "email" },
        "date": { "format": "date" },
        "url": { "format": "uri" },
        "uuid": { "format": "uuid" }
    }
}

4. Validation Tools

Online Validators

JSONLint
JSON Schema Validator
JSON Formatter & Validator

Library Options

Ajv (JavaScript)
jsonschema (Python)
json-schema-validator (Java)

5. Best Practices

Validation Guidelines

Always validate input data
Use JSON Schema for complex validation
Implement proper error handling
Validate data at multiple levels
Keep validation rules up to date

Error Handling

{
    "status": "error",
    "code": "VALIDATION_ERROR",
    "message": "Invalid input data",
    "errors": [
        {
            "field": "email",
            "message": "Invalid email format"
        },
        {
            "field": "age",
            "message": "Age must be a positive number"
        }
    ]
}