---
title: Headers
description: Using request matchers to specify which requests should respond. TODO
---
This section describes matcher functions designed to target and match HTTP headers in incoming HTTP requests.
## header
{{{docs.when.header}}}
## header_not
{{{docs.when.header_not}}}
## header_exists
{{{docs.when.header_exists}}}
## header_missing
{{{docs.when.header_missing}}}
## header_includes
{{{docs.when.header_includes}}}
## header_excludes
{{{docs.when.header_excludes}}}
## header_prefix
{{{docs.when.header_prefix}}}
## header_prefix_not
{{{docs.when.header_prefix_not}}}
## header_suffix
{{{docs.when.header_suffix}}}
## header_suffix_not
{{{docs.when.header_suffix_not}}}
## header_matches
{{{docs.when.header_matches}}}
## header_count
{{{docs.when.header_count}}}