Base64-Encoded Potential Secret Regex for JavaScript

What this pattern does

This page provides a well-structured, multi-part regular expression for matching base64-encoded potential secret, 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

// Base64-Encoded Potential Secret
// ReDoS-safe | RegexVault — Security > Secrets & Config

const base64encodedPotentialSecretRegex = /^(?:[A-Za-z0-9+\/]{4}){10,}(?:[A-Za-z0-9+\/]{2}==|[A-Za-z0-9+\/]{3}=)?$/;

function validateBase64encodedPotentialSecret(input: string): boolean {
  return base64encodedPotentialSecretRegex.test(input);
}

// Example
console.log(validateBase64encodedPotentialSecret("dGhpcyBpcyBhIHRlc3Qgc3RyaW5nIGZvciBlbmNvZGluZw==")); // true

Test Cases

When to use this pattern

This pattern is drawn from the Security > Secrets & Config 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

Pattern matches 40+ base64 characters (10+ groups of 4). High-entropy base64 strings of this length commonly represent secrets, keys, or encoded credentials. Always pair with entropy analysis — legitimate base64 text will have lower entropy than random bytes.