The word DNS is an acronym for domain name server which translates the readable domain names into numeric IP addresses. Usually your ISP assigns a DNS server for your internet connection, but you can also use many of the public DNS servers like Google public DNS and Open DNS etc. In Windows, you can use our Public DNS Server Tool to automatically set the DNS servers for your network interface cards (NICs). But once you change your DNS servers for your NIC, you have to close your web browser and restart it in order to use the new DNS servers. If you are a Firefox user, then you can use the DNS Flusher extension to avoid the restarting of the web browser and use the new DNS servers right away.
The DNS Flusher extension can be installed from the Mozilla extensions repository. The extension requires you to restart the web browser after which the extension is ready to use. It sets two new icons in the Firefox – one in the toolbar and another in the add-ons bar. The add-ons icon for DNS Flusher shows the IP address of the current website, otherwise it is exactly same as the toolbar icon. After you have changed your DNS servers, you can click on this icon in the toolbar or the add-ons bar to flush the Firefox DNS.
In the options for DNS Flusher extension (which you can open by right-clicking on the add-ons bar icon and selecting Options), you can choose to display the add-ons bar icon (status bar), reload the webpage after the DNS has been flushed and so on.
Conclusion: The DNS Flusher extension can be used to flush the Firefox DNS cache without having to close it first. It can be useful to web developers who have to manipulate the HOSTS file to test their websites.
You can download the DNS Flusher extension from https://addons.mozilla.org/en-US/firefox/addon/dns-flusher/.