---
title: "Accept header: glossary: Agent Ready HTML"
description: "Accept header defined: The request header that lists media types a client will take, with optional q weights. A dated, sourced example follows."
canonical: https://agentreadyhtml.com/glossary/accept-header/
site: "Agent Ready HTML"
last_updated: 2026-11-04
section: "Glossary"
---

# Accept header: glossary: Agent Ready HTML

> Accept header defined: The request header that lists media types a client will take, with optional q weights. A dated, sourced example follows.

Source: https://agentreadyhtml.com/glossary/accept-header/
Site: Agent Ready HTML
Last reviewed: 2026-11-04

# Accept header

In short

The request header that lists media types a client will take, with optional q weights. Example: Claude Code v2.1.38 sent Accept: text/markdown, text/html, \*/\* in Checkly's February 2026 test. Related terms: Content negotiation, Markdown negotiation, Markdown twin, Vary: Accept, AFDocs.

## Source of the example

The example in the summary above is from [checklyhq.com](https://www.checklyhq.com/blog/state-of-ai-agent-content-negotation/), read 4 November 2026.

## Where it shows up on this site

-   [Guide: serve markdown on request](https://agentreadyhtml.com/guides/serve-markdown-on-request/)

## Neighbouring terms

-   [Content negotiation](https://agentreadyhtml.com/glossary/content-negotiation/): The HTTP mechanism where the client states preferred formats in the Accept header and the server picks a representation for the same URL.
-   [Markdown negotiation](https://agentreadyhtml.com/glossary/markdown-negotiation/): Content negotiation where Accept: text/markdown returns the page as markdown with Content-Type text/markdown.
-   [Markdown twin](https://agentreadyhtml.com/glossary/markdown-twin/): A markdown copy of a page at a predictable URL, such as page.md or page.html.md.
-   [Vary: Accept](https://agentreadyhtml.com/glossary/vary-accept/): A response header telling caches that the body depends on the Accept header, so HTML and markdown are stored separately.
-   [AFDocs](https://agentreadyhtml.com/glossary/afdocs/): The Agent-Friendly Documentation spec and its open-source checker, used by Mintlify, ReadMe and GitBook docs scores.

## Sources

1.  [checklyhq.com](https://www.checklyhq.com/blog/state-of-ai-agent-content-negotation/) https://www.checklyhq.com/blog/state-of-ai-agent-content-negotation/, read 4 November 2026

Last reviewed 4 November 2026

Edition

Crawl

2026-11-04

Page updated

2026-11-04

Method

How the viewer reads a page, how a file is graded and how a platform is scored: [the method page](https://agentreadyhtml.com/method/).