How to document an HTTP header

The MDN HTTP header reference documents HTTP header fields are components of the header section of request and response messages in the Hypertext Transfer Protocol (HTTP). They define the operating parameters of an HTTP transaction. This page explains how to create a new MDN reference page for an HTTP header.

• You will need an MDN account.
• You will need to know or be able to dive into some HTTP.

• There are many HTTP headers defined in various IETF standards.
• IANA maintains a registry of headers and Wikipedia lists known header fields, but not all are relevant to web developers or part of an official standard.
• If there are red links on the current MDN header reference overview page, these headers are a good choice to document.
• If in doubt, ask an MDN contributor if you are unsure whether or not it makes sense to write about the header you have chosen.

• Existing HTTP headers are documented here.
• There are different header categories: Request header, Response header, and Representation header.
• Find the category of the header you are about to document (note that some headers can be both request and response headers, depending on context).
• Go to an existing header reference page that has the same category.

• All header pages live under this tree: /docs/Web/HTTP/Headers/
• To create a new page, see the instructions in our GitHub README.

• Either start from our template HTTP header page or use a copied structure from one of the existing HTTP header documents that you found in step 2. It's your choice.
• Write about your new HTTP header.
• Make sure you have these sections:
  • Introductory text where the first sentence mentions the header name (bold) and summarizes its purpose.
  • Information box containing at least the header type and if the header is a Forbidden header name.
  • A syntax box containing all possible directives/parameters/values of the HTTP header.
  • A section that explains these directives/values.
  • An example section that contains a practical use case for this header or shows where and how it occurs usually.
  • A specification section listing relevant RFC standard documents.
  • A "See also" section listing relevant resources.

All HTTP header pages should at least have these tags: "HTTP", "Header", "Reference".

• If you have looked at other HTTP header pages, you will see that there is a {{compat}} macro that will fill in a browser table for you.
• The compatibility table page is generated from structured data. If you'd like to contribute to the data, please check out https://github.com/mdn/browser-compat-data/README.md and send us a pull request.

• Make sure your header is listed in an appropriate category on the HTTP header reference overview page.

Once your page is created, submit it as a PR, and a member of our review team will be assigned automatically to review your page.