URL Percent-Encoding Validation Regex for JavaScript

What this pattern does

This page provides a well-structured, multi-part regular expression for matching url percent-encoding validation, 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 Percent-Encoding Validation
// ReDoS-safe | RegexVault — Web & Network > URL

const urlPercentencodingValidationRegex = /^(?:[a-zA-Z0-9\-._~!$&'()*+,;=:@\/?#\[\]]|%[0-9a-fA-F]{2})*$/;

function validateUrlPercentencodingValidation(input: string): boolean {
  return urlPercentencodingValidationRegex.test(input);
}

// Example
console.log(validateUrlPercentencodingValidation("/path/to%20resource")); // 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

This pattern validates encoding structure, not meaning. %2F is technically valid encoding but may have semantic implications (encoded forward slash vs. path separator) that require application-level handling.