Email Format Validator

What is Email Format Validation?

Email format validation (also called syntax validation) checks if an email address follows the correct structure defined by RFC 5321 standards. It verifies the email has proper syntax without actually connecting to mail servers or checking if the mailbox exists.

Email Address Structure

An email address consists of two main parts separated by an @ symbol:

RFC 5321 Rules We Check

Allowed Special Characters

Format vs Full Validation

Common Email Format Mistakes

When to Use Format Validation

• Real-time form validation (instant feedback as user types)
• Client-side validation before API calls
• Quick syntax checks without server calls
• Educational tools to teach email format rules
• Pre-screening before expensive full validation
• Privacy-focused validation (no data sent to servers)

Client-Side Implementation

Here's a simple regex for email format validation:

// Basic email format regex
const emailRegex = /^[^\s@]+@[^\s@]+\.[^\s@]+$/;

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

// Usage
isValidFormat('user@example.com');  // true
isValidFormat('invalid.email');     // false
isValidFormat('user@@example.com'); // false