Email Domain Part Only Regex for Go

What this pattern does

This page provides a comprehensive, battle-tested regular expression for matching email domain part only, ported and verified for Go. Identity and credential patterns need both correctness and safety, since they're frequent targets for adversarial input. 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

// Email Domain Part Only
// ReDoS-safe | RegexVault — Identity & PII > Email Address

package validation

import "regexp"

var emailDomainPartOnlyRe = regexp.MustCompile(`^[a-zA-Z0-9](?:[a-zA-Z0-9-]{0,61}[a-zA-Z0-9])?(?:\.[a-zA-Z0-9](?:[a-zA-Z0-9-]{0,61}[a-zA-Z0-9])?)*\.[a-zA-Z]{2,}$`)

func ValidateEmailDomainPartOnly(s string) bool {
    return emailDomainPartOnlyRe.MatchString(s)
}

// Example
// fmt.Println(ValidateEmailDomainPartOnly("example.com")) // true

Test Cases

When to use this pattern

This pattern is drawn from the Identity & PII > Email Address 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

Domain labels are max 63 chars each. Total domain max is 253 chars. Underscores are not allowed in domain names (though common in hostnames). The TLD must be 2+ letters.