Email Domain Part Only Regex for JavaScript

What this pattern does

This page provides a comprehensive, battle-tested regular expression for matching email domain part only, ported and verified for JavaScript. Identity and credential patterns need both correctness and safety, since they're frequent targets for adversarial input. The snippet below is ready to drop into your JavaScript project — whether you're validating in an Express middleware, a Next.js API route, or a client-side form.

Javascript Implementation

// Email Domain Part Only
// ReDoS-safe | RegexVault — Identity & PII > Email Address

const emailDomainPartOnlyRegex = /^[a-zA-Z0-9](?:[a-zA-Z0-9-]{0,61}[a-zA-Z0-9])?(?:\.[a-zA-Z0-9](?:[a-zA-Z0-9-]{0,61}[a-zA-Z0-9])?)*\.[a-zA-Z]{2,}$/i;

function validateEmailDomainPartOnly(input: string): boolean {
  return emailDomainPartOnlyRegex.test(input);
}

// Example
console.log(validateEmailDomainPartOnly("example.com")); // true

Test Cases

When to use this pattern

This pattern is drawn from the Identity & PII > Email Address category and carries a ReDoS-safe certification. That matters for JavaScript developers because especially critical in long-running Node.js event loops where a ReDoS vulnerability can block the entire process. RegexVault audits patterns against known backtracking attack vectors, ensuring you have the necessary context before using this regex in a high-stakes production environment.

Common Pitfalls

Technical Notes

Domain labels are max 63 chars each. Total domain max is 253 chars. Underscores are not allowed in domain names (though common in hostnames). The TLD must be 2+ letters.