This article demonstrates how to directly modify the HTTP headers that Apache sends to a client.
The Apache configuration on A2 Hosting servers includes the mod_headers module. This means that you can easily add, modify, and delete HTTP response headers by using the Header directive in an .htaccess file.
To add a custom header to the HTTP response headers, use the set or append option. The set option sets the specified header and replaces any header that has the same name. Alternatively, the append option sets the header if it does not already exist. If the header already exists, however, the append option adds to the existing header value.
For example, the following sample configuration demonstrates how to set a header and append to a header:
<IfModule mod_headers.c> Header set Animal cow Header set Animal monkey Header append Animal camel </IfModule>
In this example, the Animal header is first set to cow. But because the next header option is also set, the Animal header is reset to monkey. Lastly, camel is appended to the Animal header. This generates an HTTP response header that resembles the following:
HTTP/1.1 200 OK Date: Tue, 24 Jun 2014 15:23:33 GMT Server: Apache Animal: monkey, camel
To edit a header, use the edit option. With the edit option, you can use regular expressions to do search-and-replace operations on header values.
For example, the following sample configuration demonstrates how to do a (very) simple search-and-replace operation on a header:
<IfModule mod_headers.c> Header set Animal monkey Header append Animal camel Header edit Animal "camel" "llama" </IfModule>
In this example, camel is replaced by llama. This generates an HTTP response header that resembles the following:
HTTP/1.1 200 OK Date: Tue, 24 Jun 2014 15:42:21 GMT Server: Apache Animal: monkey, llama
To completely remove a header from an HTTP response, use the unset option.
The following sample configuration demonstrates how to remove a header:
<IfModule mod_headers.c> Header unset Animal </IfModule>
For more information about the Apache mod_headers module and the Header directive, please visit https://httpd.apache.org/docs/2.2/mod/mod_headers.html.