UUID v4 Regex for JavaScript

What this pattern does

This page provides a well-structured, multi-part regular expression for matching uuid v4, 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

// UUID v4
// ReDoS-safe | RegexVault — Web & Network > Misc

const uuidV4Regex = /^[0-9a-f]{8}-[0-9a-f]{4}-4[0-9a-f]{3}-[89ab][0-9a-f]{3}-[0-9a-f]{12}$/i;

function validateUuidV4(input: string): boolean {
  return uuidV4Regex.test(input);
}

// Example
console.log(validateUuidV4("550e8400-e29b-41d4-a716-446655440000")); // true

Test Cases

When to use this pattern

This pattern is drawn from the Web & Network > Misc 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

The 4 in position 13 (version) and the [89ab] in position 17 (variant) are the defining characteristics of UUID v4. The i flag allows uppercase hex.