IPv6 in URL Bracket Notation Regex for JavaScript

What this pattern does

This page provides a well-structured, multi-part regular expression for matching ipv6 in url bracket notation, 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 in URL Bracket Notation
// ReDoS-safe | RegexVault — Web & Network > IPv6

const ipv6InUrlBracketNotationRegex = /^\[(?:[0-9a-fA-F]{0,4}:){2,7}[0-9a-fA-F]{0,4}\]$/i;

function validateIpv6InUrlBracketNotation(input: string): boolean {
  return ipv6InUrlBracketNotationRegex.test(input);
}

// Example
console.log(validateIpv6InUrlBracketNotation("[2001:db8::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

IPv6 addresses in URLs must be in square brackets per RFC 2732. This pattern uses a simplified compressed IPv6 match — it accepts the major forms but may allow some technically invalid compressed sequences. For strict validation, pair with full IPv6 validation (net-ipv6-02) after stripping the brackets.