DNS stands for Domain Name System. It is a decentralized naming system that matches the domain names we associate with websites with their actual addresses. Any disruption in the functionality of the DNS server and users will no longer be able to open any pages in their browsers. Dealing with a 'DNS Server Unavailable' error could prove to be difficult as the issue might be caused by an actual server outage. Several alternatives exist but before getting there let's try a couple of easier troubleshoot methods.
Users encountering the 'DNS Server Unavailable' error should try another browser to check if the problem is present there as well. If the pages open normally in the other browser then go back to your preferred one and adjust its settings. Also, look for any updates that might be available to bring its version to the latest that has been released. If the error persists across multiple browsers, the next potential fix is to restart your router. Go to the device, unplug it, and wait for several seconds before plugging it back in again. Check if the DNS error has disappeared.
Lastly, if the issue is indeed caused by the current DNS server, users might want to try and change to a different one. This method will need you to access your router's settings. Usually, the default login credentials will be printed on the device itself. To access the management interface, however, you have to type the IP address of the router into your browser. Once inside, go to the DNS settings and enter the details of a new server. Some suitable choices are Google's DNS server and OpenDNS:
Google DNS: 18.104.22.168. and 22.214.171.124.
OpenDNS: 126.96.36.199 and 188.8.131.52
Hopefully, this has fixed the 'DNS Server Unavailable' error.