Windows UNC Path Regex for JavaScript

What this pattern does

This page provides a comprehensive, battle-tested regular expression for matching windows unc path, 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

// Windows UNC Path
// ReDoS-safe | RegexVault — Dev & Systems > File Paths

const windowsUncPathRegex = /^\\{4}(?!\\)(?:[^\\\/:*?"<>|\r\n]+(?:\\{1,2}|\\/))+[^\\\/:*?"<>|\r\n]+$/;

function validateWindowsUncPath(input: string): boolean {
  return windowsUncPathRegex.test(input);
}

// Example
console.log(validateWindowsUncPath("\\\\server\\share")); // true

Test Cases

When to use this pattern

This pattern is drawn from the Dev & Systems > File Paths 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

Groups: 1=server name, 2=share name. Administrative shares end with $ (C$, ADMIN$). Avoid constructing UNC paths from user input — they can be used to capture NTLM hashes.