Virtual Hosts is a Firefox add-on designed for web developers needing to access virtual hosts on a server without altering host redirection or DNS settings. This subscription-based tool allows for the overwriting of the 'Host' HTTP header, facilitating the request of specific virtual hosts from remote web servers. It is particularly useful during DNS propagation periods or when setting up replacement sites, providing a hassle-free alternative to manually editing the hosts file.

The extension operates by intercepting outgoing HTTP(S) requests from the Firefox browser, rewriting the Host header to match the specified virtual host domain. Users can easily enable or disable the add-on through a simple interface, adding new virtual hosts as needed. It's important to note that this tool does not resolve DNS to IP but focuses on HTTP virtual hosting, making it essential for developers looking to streamline their testing processes.