Regex Email Validation Pattern — Test & Examples

Email validation is one of the most common uses of regular expressions. But finding the right regex pattern is tricky — too simple and you miss valid emails, too complex and you reject legitimate addresses. This guide provides three levels of email regex patterns with test cases, plus implementation examples in JavaScript, Python, and C#.

Level 1: Simple Pattern (Most Common)

This pattern covers 99% of real-world email addresses and is the best balance of accuracy and readability:

^[a-zA-Z0-9._%+-]+@[a-zA-Z0-9.-]+\.[a-zA-Z]{2,}$Regex

What it matches:

✅ [email protected]
✅ [email protected]
✅ [email protected]
✅ [email protected]
✅ [email protected]
❌ @example.com          (no local part)
❌ user@                 (no domain)
❌ [email protected]             (dot at domain start)
❌ user [email protected] (spaces not allowed)Test Cases

Level 2: Stricter Pattern

Adds length restrictions and prevents consecutive dots:

^[a-zA-Z0-9](?:[a-zA-Z0-9._%+-]{0,62}[a-zA-Z0-9])?@[a-zA-Z0-9](?:[a-zA-Z0-9-]{0,61}[a-zA-Z0-9])?(?:\.[a-zA-Z]{2,})+$Regex

Level 3: RFC 5322 (Complete but Complex)

The full RFC 5322 email regex is incredibly complex and rarely needed in practice:

(?:[a-z0-9!#$%&'*+/=?^_`{|}~-]+(?:\.[a-z0-9!#$%&'*+/=?^_`{|}~-]+)*|"(?:[\x01-\x08\x0b\x0c\x0e-\x1f\x21\x23-\x5b\x5d-\x7f]|\\[\x01-\x09\x0b\x0c\x0e-\x7f])*")@(?:(?:[a-z0-9](?:[a-z0-9-]*[a-z0-9])?\.)+[a-z0-9](?:[a-z0-9-]*[a-z0-9])?|\[(?:(?:25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)\.){3}(?:25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?|[a-z0-9-]*[a-z0-9]:(?:[\x01-\x08\x0b\x0c\x0e-\x1f\x21-\x5a\x53-\x7f]|\\[\x01-\x09\x0b\x0c\x0e-\x7f])+)\])RFC 5322 Regex

Implementation Examples

JavaScript

const emailRegex = /^[a-zA-Z0-9._%+-]+@[a-zA-Z0-9.-]+\.[a-zA-Z]{2,}$/;

function validateEmail(email) {
    return emailRegex.test(email);
}

// HTML5 built-in validation (easier approach):
// <input type="email" required>JavaScript

Python

import re

EMAIL_PATTERN = re.compile(
    r'^[a-zA-Z0-9._%+-]+@[a-zA-Z0-9.-]+\.[a-zA-Z]{2,}$'
)

def validate_email(email: str) -> bool:
    return bool(EMAIL_PATTERN.match(email))

# Better approach for production:
# pip install email-validator
from email_validator import validate_email, EmailNotValidErrorPython

C#

using System.Text.RegularExpressions;

public static partial class EmailValidator
{
    [GeneratedRegex(@"^[a-zA-Z0-9._%+-]+@[a-zA-Z0-9.-]+\.[a-zA-Z]{2,}$")]
    private static partial Regex EmailRegex();

    public static bool IsValid(string email)
        => EmailRegex().IsMatch(email);
}

// .NET built-in (recommended):
// System.Net.Mail.MailAddress.TryCreate(email, out _)C#

Production Best Practices

• Regex is not enough — use it only for basic format validation on the frontend
• Always send a verification email — the only way to confirm an email exists
• Don't be too strict — you'll reject valid emails from new TLDs like .museum or .company
• Use platform validators — MailAddress.TryCreate() in .NET, email-validator in Python, HTML5 <input type="email"> in browsers
• Consider internationalized emails — RFC 6531 allows Unicode in local parts (e.g., 用户@example.com)

Conclusion

For email validation, the simple pattern ^[a-zA-Z0-9._%+-]+@[a-zA-Z0-9.-]+\.[a-zA-Z]{2,}$ is the best choice for most applications. Combine it with server-side verification for production use. Test your patterns using Polymorpher's Regex Tester, and check out our 10 Regex Patterns Every Developer Should Know for more patterns.