IPv4 Address (as PII identifier) Regex for JavaScript

What this pattern does

This page provides a comprehensive, battle-tested regular expression for matching ipv4 address (as pii identifier), ported and verified for JavaScript. Identity and credential patterns need both correctness and safety, since they're frequent targets for adversarial input. 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

// IPv4 Address (as PII identifier)
// ReDoS-safe | RegexVault — Identity & PII > Digital Identity

const ipv4AddressAsPiiIdentifierRegex = /^(?:(?:25[0-5]|2[0-4][0-9]|1[0-9]{2}|[1-9][0-9]|[0-9])\.){3}(?:25[0-5]|2[0-4][0-9]|1[0-9]{2}|[1-9][0-9]|[0-9])$/;

function validateIpv4AddressAsPiiIdentifier(input: string): boolean {
  return ipv4AddressAsPiiIdentifierRegex.test(input);
}

// Example
console.log(validateIpv4AddressAsPiiIdentifier("192.168.1.1")); // true

Test Cases

When to use this pattern

This pattern is drawn from the Identity & PII > Digital Identity 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

Under GDPR (C-582/14, Breyer v Germany), IP addresses can constitute personal data when the controller has the legal means to identify the individual. Dynamic IPs assigned by ISPs are personal data. Log files containing IP addresses must comply with GDPR retention requirements.