PKCE Code Verifier Regex for Go

What this pattern does

This page provides a lightweight, single-purpose regular expression for matching pkce code verifier, ported and verified for Go. In security-sensitive code, using an unverified regex can open the door to both false positives and denial-of-service attacks. 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

// PKCE Code Verifier
// ReDoS-safe | RegexVault — Security > OAuth & OIDC

package validation

import "regexp"

var pkceCodeVerifierRe = regexp.MustCompile(`^[A-Za-z0-9\-._~]{43,128}$`)

func ValidatePkceCodeVerifier(s string) bool {
    return pkceCodeVerifierRe.MatchString(s)
}

// Example
// fmt.Println(ValidatePkceCodeVerifier("dBjftJeZ4CVP-mB92K27uhbUJU1p1r_wW1gFWFOEjXk")) // true

Test Cases

When to use this pattern

This pattern is drawn from the Security > OAuth & OIDC 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

RFC 7636 PKCE: code_verifier is a random string 43-128 chars from [A-Za-z0-9-._~]. code_challenge = BASE64URL(SHA256(code_verifier)) for S256 method. PKCE is mandatory for public clients (SPAs, mobile apps) and recommended for all clients.