PKCE Code Verifier Regex for JavaScript

What this pattern does

This page provides a lightweight, single-purpose regular expression for matching pkce code verifier, ported and verified for JavaScript. 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 JavaScript project — whether you're validating in an Express middleware, a Next.js API route, or a client-side form.

Javascript Implementation

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

const pkceCodeVerifierRegex = /^[A-Za-z0-9\-._~]{43,128}$/;

function validatePkceCodeVerifier(input: string): boolean {
  return pkceCodeVerifierRegex.test(input);
}

// Example
console.log(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 JavaScript developers because especially critical in long-running Node.js event loops where a ReDoS vulnerability can block the entire process. 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.