MD5 Hash (Deprecated — Detection Only) Regex for JavaScript

What this pattern does

This page provides a lightweight, single-purpose regular expression for matching md5 hash (deprecated — detection only), 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

// MD5 Hash (Deprecated — Detection Only)
// ReDoS-safe | RegexVault — Security > Password Formats

const md5HashDeprecatedDetectionOnlyRegex = /^[a-f0-9]{32}$/i;

function validateMd5HashDeprecatedDetectionOnly(input: string): boolean {
  return md5HashDeprecatedDetectionOnlyRegex.test(input);
}

// Example
console.log(validateMd5HashDeprecatedDetectionOnly("d41d8cd98f00b204e9800998ecf8427e")); // 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

MD5 is cryptographically broken — collision attacks are trivial, preimage attacks are feasible. Never use MD5 for password hashing or security purposes. Use only for checksums where collision resistance is not required (e.g., non-security file deduplication). Include this pattern only for detection/migration purposes.