Base64 URL-Safe (No Padding) Regex for JavaScript

What this pattern does

This page provides a lightweight, single-purpose regular expression for matching base64 url-safe (no padding), ported and verified for JavaScript. A rigorously tested regex reduces debugging time and protects your application from edge-case failures. 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

// Base64 URL-Safe (No Padding)
// ReDoS-safe | RegexVault — Web & Network > Misc

const base64UrlsafeNoPaddingRegex = /^[A-Za-z0-9\-_]+$/;

function validateBase64UrlsafeNoPadding(input: string): boolean {
  return base64UrlsafeNoPaddingRegex.test(input);
}

// Example
console.log(validateBase64UrlsafeNoPadding("SGVsbG8")); // true

Test Cases

When to use this pattern

This pattern is drawn from the Web & Network > Misc 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

Used in JWTs, OAuth tokens, and URL-embedded data. Empty string is excluded here since a zero-length token is semantically invalid in most use cases.