scrypt Hash (passlib format) Regex for JavaScript

What this pattern does

This page provides a comprehensive, battle-tested regular expression for matching scrypt hash (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

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

const scryptHashPasslibFormatRegex = /^\$scrypt\$ln=([0-9]+),r=([0-9]+),p=([0-9]+)\$([A-Za-z0-9+\/]{16,64}(?:={0,2}))\$([A-Za-z0-9+\/]{30,64}(?:={0,1}))$/;

function validateScryptHashPasslibFormat(input: string): boolean {
  return scryptHashPasslibFormatRegex.test(input);
}

// Example
console.log(validateScryptHashPasslibFormat("$scrypt$ln=14,r=8,p=1$aM15816PilIJep0o$nFNh2CVHVjNldFVKDHDlm0248RZvVaR8")); // 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

Parameters: ln=log2(N) where N is the work factor, r=block size (8), p=parallelism (1). OWASP recommends N=32768 (ln=15), r=8, p=1 minimum. scrypt is memory-hard like Argon2, designed by Colin Percival. ln=14 = N=16384.