PBKDF2 Hash (Django / passlib format) Regex for JavaScript

What this pattern does

This page provides a well-structured, multi-part regular expression for matching pbkdf2 hash (django / passlib format), 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

// PBKDF2 Hash (Django / passlib format)
// ReDoS-safe | RegexVault — Security > Password Formats

const pbkdf2HashDjangoPasslibFormatRegex = /^pbkdf2_sha(256|512)\$([0-9]+)\$([A-Za-z0-9+\/=]{1,32})\$([A-Za-z0-9+\/=]{43,86})$/;

function validatePbkdf2HashDjangoPasslibFormat(input: string): boolean {
  return pbkdf2HashDjangoPasslibFormatRegex.test(input);
}

// Example
console.log(validatePbkdf2HashDjangoPasslibFormat("pbkdf2_sha256$390000$abcdefghijklmnop$abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMN01234567890=")); // true

Test Cases

When to use this pattern

This pattern is drawn from the Security > Password Formats 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

Format: algorithm + $ + iterations + $ + salt (base64) + $ + hash (base64). Django default uses sha256 with 390000 iterations (Django 4.2). NIST SP 800-63b recommends at least 10000 iterations — modern systems should use much higher. SHA-512 is preferred over SHA-256.