OAuth 2.0 Refresh Token (Generic) Regex for JavaScript

What this pattern does

This page provides a lightweight, single-purpose regular expression for matching oauth 2.0 refresh token (generic), 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

// OAuth 2.0 Refresh Token (Generic)
// ReDoS-safe | RegexVault — Security > OAuth & OIDC

const oauth20RefreshTokenGenericRegex = /^[A-Za-z0-9\-_.+\/=]{40,512}$/;

function validateOauth20RefreshTokenGeneric(input: string): boolean {
  return oauth20RefreshTokenGenericRegex.test(input);
}

// Example
console.log(validateOauth20RefreshTokenGeneric("1//0gBcDeFgHiJkLmNoPqRsTuVwXyZ01234567890aBcDeFgHiJkLmNoPqR")); // 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

Refresh tokens are long-lived (hours to years) credentials used to obtain new access tokens. They must be stored securely (not in localStorage or cookies without Secure/HttpOnly flags). Rotation on use (refresh token rotation) is best practice.