Email Regex Pattern API: Validate Email Addresses Correctly

Need a reliable regex pattern for email validation? This guide covers the Email Regex Pattern API, which provides battle-tested patterns for validating email addresses, from simple practical patterns to full RFC 5322 compliance.

The Email Validation Challenge

Email validation is surprisingly complex. A fully RFC-compliant email regex is thousands of characters long, yet even simple patterns work for 99% of real-world cases. The challenge is balancing strictness with practicality.

Valid emails can include unusual characters: "john..doe"@example.com and admin@[192.168.1.1] are technically valid!

Pattern Types

The API provides different pattern types for various needs:

• Simple: Basic pattern for most common emails
• Standard: Good balance of accuracy and complexity (recommended)
• Strict: More comprehensive validation
• RFC 5322: Full RFC compliance (very complex)

Using the Email Regex API

TinyFn provides pre-built email validation patterns:

GET https://api.tinyfn.io/v1/regex/patterns/email
Headers: X-API-Key: your-api-key

{
  "pattern": "^[a-zA-Z0-9._%+-]+@[a-zA-Z0-9.-]+\\.[a-zA-Z]{2,}$",
  "type": "standard",
  "description": "Standard email validation pattern for common use cases",
  "flags": "i",
  "examples": {
    "valid": ["user@example.com", "name.surname@company.co.uk"],
    "invalid": ["invalid", "@example.com", "user@.com"]
  }
}

Parameters

Code Examples

JavaScript / Node.js

// Get the email pattern
const response = await fetch(
  'https://api.tinyfn.io/v1/regex/patterns/email?type=standard',
  { headers: { 'X-API-Key': 'your-api-key' } }
);
const { pattern, flags } = await response.json();

// Use it for validation
const emailRegex = new RegExp(pattern, flags);
console.log(emailRegex.test('user@example.com')); // true
console.log(emailRegex.test('invalid-email')); // false

Python

import requests
import re

response = requests.get(
    'https://api.tinyfn.io/v1/regex/patterns/email',
    params={'type': 'strict'},
    headers={'X-API-Key': 'your-api-key'}
)
result = response.json()

# Compile and use the pattern
email_pattern = re.compile(result['pattern'], re.IGNORECASE)
print(bool(email_pattern.match('user@example.com')))  # True
print(bool(email_pattern.match('user@localhost')))  # False (no TLD)

cURL

curl "https://api.tinyfn.io/v1/regex/patterns/email?type=simple" \
  -H "X-API-Key: your-api-key"

Common Use Cases

• Form Validation: Validate email inputs before submission
• Data Cleaning: Filter valid emails from datasets
• Email Extraction: Find emails in text (use unanchored pattern)
• Input Masking: Guide users toward valid email format
• API Validation: Validate email parameters in requests

Best Practices

1. Don't rely solely on regex: Send a confirmation email for true validation
2. Allow plus addressing: Patterns should allow user+tag@example.com
3. Support international TLDs: Modern TLDs can be longer than 3 characters
4. Trim whitespace: Trim input before validation

Use via MCP

Your AI agent can call this tool directly via Model Context Protocol — no HTTP code needed. Add TinyFn to Claude Desktop, Cursor, or any MCP client:

{
  "mcpServers": {
    "tinyfn-regex": {
      "url": "https://api.tinyfn.io/mcp/regex/",
      "headers": {
        "X-API-Key": "your-api-key"
      }
    }
  }
}

See all regex tools available via MCP in our Regex MCP Tools for AI Agents guide.