Docker Registry URL Regex for JavaScript

What this pattern does

This page provides a well-structured, multi-part regular expression for matching docker registry url, 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

// Docker Registry URL
// ReDoS-safe | RegexVault — Dev & Systems > Docker

const dockerRegistryUrlRegex = /^(?:[a-z0-9][a-z0-9\-]*\.)+[a-z]{2,63}(?::[1-9][0-9]{0,4})?$/;

function validateDockerRegistryUrl(input: string): boolean {
  return dockerRegistryUrlRegex.test(input);
}

// Example
console.log(validateDockerRegistryUrl("docker.io")); // true

Test Cases

When to use this pattern

This pattern is drawn from the Dev & Systems > Docker 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

Docker registry URLs do not include a scheme in image references. Port 5000 is the default for private registry deployments. 'localhost' is a Docker special case not matched by this pattern.