Docker Image Tag Regex for JavaScript

What this pattern does

This page provides a well-structured, multi-part regular expression for matching docker image tag, 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 Image Tag
// ReDoS-safe | RegexVault — Dev & Systems > Docker

const dockerImageTagRegex = /^[a-zA-Z0-9][a-zA-Z0-9._\-]{0,127}$/;

function validateDockerImageTag(input: string): boolean {
  return dockerImageTagRegex.test(input);
}

// Example
console.log(validateDockerImageTag("latest")); // 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

Tags cannot start with a period or hyphen. 'latest' is the default tag if none is specified. Always pin to a digest (sha256:...) for reproducible deployments in production.