Domain Label (Single Segment) Regex for Go

What this pattern does

This page provides a well-structured, multi-part regular expression for matching domain label (single segment), 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

// Domain Label (Single Segment)
// ReDoS-safe | RegexVault — Web & Network > Domain

package validation

import "regexp"

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

func ValidateDomainLabelSingleSegment(s string) bool {
    return domainLabelSingleSegmentRe.MatchString(s)
}

// Example
// fmt.Println(ValidateDomainLabelSingleSegment("example")) // true

Test Cases

When to use this pattern

This pattern is drawn from the Web & Network > Domain 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

The 63-character maximum is per RFC 1034. The last invalid test case is 64 chars (one over the limit). Use for validating individual hostname components.