MAC Address (Colon-Separated, Lowercase) Regex for JavaScript

What this pattern does

This page provides a well-structured, multi-part regular expression for matching mac address (colon-separated, lowercase), ported and verified for JavaScript. A rigorously tested regex reduces debugging time and protects your application from edge-case failures. 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

// MAC Address (Colon-Separated, Lowercase)
// ReDoS-safe | RegexVault — Web & Network > MAC Address

const macAddressColonseparatedLowercaseRegex = /^[0-9a-f]{2}(?::[0-9a-f]{2}){5}$/;

function validateMacAddressColonseparatedLowercase(input: string): boolean {
  return macAddressColonseparatedLowercaseRegex.test(input);
}

// Example
console.log(validateMacAddressColonseparatedLowercase("00:1a:2b:3c:4d:5e")); // true

Test Cases

When to use this pattern

This pattern is drawn from the Web & Network > MAC 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

Lowercase only. For case-insensitive matching, use net-mac-02. Broadcast MAC is ff:ff:ff:ff:ff:ff. The null/unset MAC is 00:00:00:00:00:00.