IPv6 Loopback Address Regex for JavaScript

What this pattern does

This page provides a lightweight, single-purpose regular expression for matching ipv6 loopback address, 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

// IPv6 Loopback Address
// ReDoS-safe | RegexVault — Web & Network > IPv6

const ipv6LoopbackAddressRegex = /^(?:::1|(?:0{1,4}:){7}0*1)$/i;

function validateIpv6LoopbackAddress(input: string): boolean {
  return ipv6LoopbackAddressRegex.test(input);
}

// Example
console.log(validateIpv6LoopbackAddress("::1")); // true

Test Cases

When to use this pattern

This pattern is drawn from the Web & Network > IPv6 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

Prefer ::1 normalization in storage. The pattern accepts expanded forms for input validation but ::1 is the canonical representation per RFC 5952.