Content-Type MIME Type Regex for JavaScript

What this pattern does

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

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

const contenttypeMimeTypeRegex = /^[a-zA-Z][a-zA-Z0-9!#$&\-^_]{0,59}\/[a-zA-Z][a-zA-Z0-9!#$&\-^_.+]{0,59}(?:;\s*[a-zA-Z][a-zA-Z0-9\-]{0,49}=[^;\s]{1,100})*$/i;

function validateContenttypeMimeType(input: string): boolean {
  return contenttypeMimeTypeRegex.test(input);
}

// Example
console.log(validateContenttypeMimeType("application/json")); // true

Test Cases

When to use this pattern

This pattern is drawn from the Web & Network > HTTP 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

Parameters use name=value format separated by semicolons. The charset parameter is the most common. IANA maintains the media type registry.