Email Address (RFC 5321 Practical) Regex for JavaScript

What this pattern does

This page provides a comprehensive, battle-tested regular expression for matching email address (rfc 5321 practical), 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 Address (RFC 5321 Practical)
// ReDoS-safe | RegexVault — Identity & PII > Email Address

const emailAddressRfc5321PracticalRegex = /^[a-zA-Z0-9.!#$%&'*+\/=?^_`{|}~-]+@[a-zA-Z0-9](?:[a-zA-Z0-9-]{0,61}[a-zA-Z0-9])?(?:\.[a-zA-Z0-9](?:[a-zA-Z0-9-]{0,61}[a-zA-Z0-9])?)*\.[a-zA-Z]{2,}$/i;

function validateEmailAddressRfc5321Practical(input: string): boolean {
  return emailAddressRfc5321PracticalRegex.test(input);
}

// Example
console.log(validateEmailAddressRfc5321Practical("user@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

Deliberately excludes quoted strings and IP address literals (RFC 5321 allows them but they are vanishingly rare in practice). The TLD must be at least 2 letters. Internationalized domain names (IDN) require Punycode encoding first.