Well-Known Port (1–1023) Regex for JavaScript

What this pattern does

This page provides a well-structured, multi-part regular expression for matching well-known port (1–1023), ported and verified for JavaScript. A rigorously tested regex reduces debugging time and protects your application from edge-case failures. 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

// Well-Known Port (1–1023)
// ReDoS-safe | RegexVault — Web & Network > Port

const wellknownPort11023Regex = /^(?:102[0-3]|10[01][0-9]|[1-9][0-9]{0,2})$/;

function validateWellknownPort11023(input: string): boolean {
  return wellknownPort11023Regex.test(input);
}

// Example
console.log(validateWellknownPort11023("1")); // true

Test Cases

When to use this pattern

This pattern is drawn from the Web & Network > Port 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

Common well-known ports: 21 (FTP), 22 (SSH), 25 (SMTP), 53 (DNS), 80 (HTTP), 443 (HTTPS). Full list maintained by IANA.