Full Query String Regex for JavaScript

What this pattern does

This page provides a comprehensive, battle-tested regular expression for matching full query string, 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

// Full Query String
// ReDoS-safe | RegexVault — Web & Network > URL

const fullQueryStringRegex = /^\?(?:[a-zA-Z0-9_\-.~%+]+(?:=[a-zA-Z0-9_\-.~%+:@!$'()*,;\/?]*)?(?:&[a-zA-Z0-9_\-.~%+]+(?:=[a-zA-Z0-9_\-.~%+:@!$'()*,;\/?]*)?)*)?(?=$|#|\s)$/;

function validateFullQueryString(input: string): boolean {
  return fullQueryStringRegex.test(input);
}

// Example
console.log(validateFullQueryString("?key=value")); // 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

Bare ? (empty query string) is valid per RFC 3986. Key-only parameters without = are also valid (e.g., ?flag). Use in combination with URL host matching for full URL validation.