Unix Relative Path (Safe) Regex for JavaScript

What this pattern does

This page provides a comprehensive, battle-tested regular expression for matching unix relative path (safe), 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

// Unix Relative Path (Safe)
// ReDoS-safe | RegexVault — Dev & Systems > File Paths

const unixRelativePathSafeRegex = /^(?!\/)(?!.*\.\.)[a-zA-Z0-9._\-~][a-zA-Z0-9._\-~\/]*$/;

function validateUnixRelativePathSafe(input: string): boolean {
  return unixRelativePathSafeRegex.test(input);
}

// Example
console.log(validateUnixRelativePathSafe("src/main.go")); // 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

Explicitly rejects absolute paths and traversal sequences. Use for validating relative paths in file upload handlers or ZIP extraction routines. Zip Slip vulnerability exploits exactly this.