IPv4-Mapped IPv6 Address Regex for Go

What this pattern does

This page provides a comprehensive, battle-tested regular expression for matching ipv4-mapped ipv6 address, ported and verified for Go. A rigorously tested regex reduces debugging time and protects your application from edge-case failures. The snippet below is ready to drop into your Go project — whether you're validating in a Gin handler, a gRPC service, or a command-line tool.

Go Implementation

// IPv4-Mapped IPv6 Address
// ReDoS-safe | RegexVault — Web & Network > IPv6

package validation

import "regexp"

var ipv4mappedIpv6AddressRe = regexp.MustCompile(`^::(?:ffff:)?(?:(?:25[0-5]|2[0-4][0-9]|1[0-9]{2}|[1-9][0-9]|[0-9])\.){3}(?:25[0-5]|2[0-4][0-9]|1[0-9]{2}|[1-9][0-9]|[0-9])$`)

func ValidateIpv4mappedIpv6Address(s string) bool {
    return ipv4mappedIpv6AddressRe.MatchString(s)
}

// Example
// fmt.Println(ValidateIpv4mappedIpv6Address("::ffff:192.168.1.1")) // 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 Go developers because Go's RE2 engine is inherently safe from catastrophic backtracking, but this pattern has been additionally verified for correctness. 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

Used when a dual-stack socket receives an IPv4 connection. The ::ffff: prefix indicates the IPv4-mapped form. Without ffff, it is an IPv4-compatible address (deprecated per RFC 4291).