MIME Type Regex for JavaScript

What this pattern does

This page provides a comprehensive, battle-tested regular expression for matching mime type, 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

// MIME Type
// ReDoS-safe | RegexVault — Web & Network > Misc

const mimeTypeRegex = /^(?:application|audio|font|image|model|multipart|text|video|message|x-[a-zA-Z0-9][a-zA-Z0-9!#$&\-^_]{0,30})\/[a-zA-Z][a-zA-Z0-9!#$&\-^_.+]{0,100}(?:;\s*[a-zA-Z][a-zA-Z0-9\-]{0,30}=[^;\s]{1,50})*$/i;

function validateMimeType(input: string): boolean {
  return mimeTypeRegex.test(input);
}

// Example
console.log(validateMimeType("text/html")); // 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

Top-level type is validated against IANA-defined values. x- prefix allows vendor/experimental types. Subtype may include vendor tree (vnd.), personal tree (prs.), or standard tree.