Windows Absolute Path (Drive Letter) Regex for PHP

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 PHP. A rigorously tested regex reduces debugging time and protects your application from edge-case failures. The snippet below is ready to drop into your PHP project — whether you're validating in a Laravel validator, a WordPress plugin, or a standalone PHP script.

Php Implementation

<?php
// Windows Absolute Path (Drive Letter)
// ReDoS-safe | RegexVault — Dev & Systems > File Paths

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

function validate_windows_absolute_path_drive_letter(string $input): bool {
    return (bool) preg_match(WINDOWS_ABSOLUTE_PATH_DRIVE_LETTER_PATTERN, $input);
}

// Example
var_dump(validate_windows_absolute_path_drive_letter("C:\\Users\\user\\Documents")); // bool(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 PHP developers because especially relevant in PHP where PCRE backtracking limits can trigger silent failures on malicious input. 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.