URL Host Extraction Regex for JavaScript

What this pattern does

This page provides a comprehensive, battle-tested regular expression for matching url host extraction, 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

// URL Host Extraction
// ReDoS-safe | RegexVault — Web & Network > URL

const urlHostExtractionRegex = /^[a-zA-Z][a-zA-Z0-9+\-.]{0,20}:\/\/(?:[^@\/\s]+@)?([a-zA-Z0-9\-._\[\]]+)(?::[0-9]+)?(?:\/[^\s]*)?$/i;

function validateUrlHostExtraction(input: string): boolean {
  return urlHostExtractionRegex.test(input);
}

// Example
console.log(validateUrlHostExtraction("https://example.com")); // true

Test Cases

When to use this pattern

This pattern is drawn from the Web & Network > URL 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

Capture group 1 contains the hostname or IP (including IPv6 brackets if present). Handles optional auth prefix before @.