Windows Absolute Path (Drive Letter) Regex for JavaScript

What this pattern does

This page provides a well-structured, multi-part regular expression for matching windows absolute path (drive letter), 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 Absolute Path (Drive Letter)
// ReDoS-safe | RegexVault — Dev & Systems > File Paths

const windowsAbsolutePathDriveLetterRegex = /^[a-zA-Z]:(?:\\{1,2}|\\/)(?:[^\\\/:*?"<>|\r\n]+(?:\\{1,2}|\\/))*[^\\\/:*?"<>|\r\n]*$/;

function validateWindowsAbsolutePathDriveLetter(input: string): boolean {
  return windowsAbsolutePathDriveLetterRegex.test(input);
}

// Example
console.log(validateWindowsAbsolutePathDriveLetter("C:\\Users\\user\\Documents")); // 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

Windows reserved characters < > : " | ? * are excluded. The pattern accepts both backslash and forward slash. Drive letters are A-Z. UNC paths (\\\\server\\share) require dev-path-06.