HTTP Header Field Name Regex for JavaScript

What this pattern does

This page provides a well-structured, multi-part regular expression for matching http header field name, 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

// HTTP Header Field Name
// ReDoS-checked | RegexVault — Web & Network > HTTP

const httpHeaderFieldNameRegex = /^[a-zA-Z][a-zA-Z0-9\-!#$%&'*+.^_`|~]{0,99}$/;

function validateHttpHeaderFieldName(input: string): boolean {
  return httpHeaderFieldNameRegex.test(input);
}

// Example
console.log(validateHttpHeaderFieldName("Content-Type")); // true

Test Cases

When to use this pattern

This pattern is drawn from the Web & Network > HTTP category and has been checked for ReDoS risk. 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

HTTP header names are case-insensitive per RFC 7230 but conventionally Title-Case. Reject headers with spaces — they indicate header injection attempts.