IPv6 Full (Expanded + Compressed) Regex for PHP

What this pattern does

This page provides a comprehensive, battle-tested regular expression for matching ipv6 full (expanded + compressed), ported and verified for PHP. A rigorously tested regex reduces debugging time and protects your application from edge-case failures. The snippet below is ready to drop into your PHP project — whether you're validating in a Laravel validator, a WordPress plugin, or a standalone PHP script.

Php Implementation

<?php
// IPv6 Full (Expanded + Compressed)
// ReDoS-safe | RegexVault — Web & Network > IPv6

define('IPV6_FULL_EXPANDED_COMPRESSED_PATTERN', '/^(([0-9a-fA-F]{1,4}:){7}[0-9a-fA-F]{1,4}|([0-9a-fA-F]{1,4}:){1,7}:|([0-9a-fA-F]{1,4}:){1,6}:[0-9a-fA-F]{1,4}|([0-9a-fA-F]{1,4}:){1,5}(:[0-9a-fA-F]{1,4}){1,2}|([0-9a-fA-F]{1,4}:){1,4}(:[0-9a-fA-F]{1,4}){1,3}|([0-9a-fA-F]{1,4}:){1,3}(:[0-9a-fA-F]{1,4}){1,4}|([0-9a-fA-F]{1,4}:){1,2}(:[0-9a-fA-F]{1,4}){1,5}|[0-9a-fA-F]{1,4}:(:[0-9a-fA-F]{1,4}){1,6}|:(:[0-9a-fA-F]{1,4}){1,7}|::)$/');

function validate_ipv6_full_expanded_compressed(string $input): bool {
    return (bool) preg_match(IPV6_FULL_EXPANDED_COMPRESSED_PATTERN, $input);
}

// Example
var_dump(validate_ipv6_full_expanded_compressed("2001:db8::1")); // bool(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 PHP developers because especially relevant in PHP where PCRE backtracking limits can trigger silent failures on malicious input. 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

Each alternation handles a specific number of groups before/after ::. The :: can appear at most once (enforced by alternation structure, not lookahead). Go's RE2 may have issues with alternation of this complexity — use net.ParseIP() in Go instead.