Password Policy Strength Check Regex for JavaScript

What this pattern does

This page provides a comprehensive, battle-tested regular expression for matching password policy strength check, 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

// Password Policy Strength Check
// ReDoS-safe | RegexVault — Security > Password Formats

const passwordPolicyStrengthCheckRegex = /^(?=.*[a-z])(?=.*[A-Z])(?=.*[0-9])(?=.*[!@#$%^&*()_+\-=\[\]{};':"\\|,.<>\\/?~`])(?!.*\s).{12,128}$/;

function validatePasswordPolicyStrengthCheck(input: string): boolean {
  return passwordPolicyStrengthCheckRegex.test(input);
}

// Example
console.log(validatePasswordPolicyStrengthCheck("Correct!Horse#Battery9")); // true

Test Cases

When to use this pattern

This pattern is drawn from the Security > Password Formats category and is provided for complex validation requirements. 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

NIST SP 800-63b (2017) de-emphasized complexity rules in favor of length and breach database checking. This pattern implements the more traditional complexity approach. Minimum 12 characters is NIST-aligned. 128-char maximum prevents DoS via extremely long inputs.