DNS Cache: It is known that the Internet has many secrets. It has many functions that are not obvious to the average user. Accessing a website, for example, may seem simple, but it is a complex process with many steps. This process has been optimized so much that it takes milliseconds to complete.
However, behind the screen of your computer, as well as on other computers, a lot happens. One of these is the DNS cache.
DNS is the service that connects the domain name of a page with the IP address.
DNS Sketch
Every page on the web doesn't just have an easy-to-remember name. It also has an IP address, which is much harder to remember. This address "shows" the identity of the server that hosts the page.
That's where the DNS service comes in. It works in the background and connects an IP address to the name of the page that we type into our browser's URL to connect to it.
DNS Cache
To make the DNS service work much faster, the DNS cache or DNS cache was also created. The name gives an indication of what it does, but we will see it better.
Essentially, the DNS cache keeps a history of the pages you have visited. It knows that, for example, you have visited secnews.gr and remembers which IP address corresponds to this specific domain. The DNS cache helps the DNS service not have to search again and again for the addresses of the websites you visit frequently.
So when you type an address, it first checks the cache and if it is there, it serves it without delay. If the address does not exist because you are visiting a page for the first time, the request will be sent to the DNS service to be resolved.
The DNS cache is maintained by your operating system. But browsers also have a DNS cache. It helps them to be faster. So if, for example, you are using Chrome and you view a page, the Google browser will first check its own DNS cache.
DNS cache problems
DNS caches, especially browser caches, can become corrupted. This can happen at any time. If the cache hasn't been refreshed for a long time, it can lead to websites not loading.
There's also DNS poisoning. It's caused by malicious websites that insert new malicious files or corrupt the cache. What can cause this?
You want to visit Facebook, but you don't visit Facebook. DNS poisoning will take you to a page that looks like Facebook, but it's not.
So below we'll look at what you can do when the DNS cache on your computer, or in the browser you're using, is corrupted.
Delete DNS cache
Chrome
To clear the DNS cache in Chrome, type the following in the address bar and click the 'Clear Cache' button.
chrome://net-internals/#dns
Firefox
Open Firefox and type about:config in the address bar. Accept the warning in the box that appears to proceed to Firefox settings. Search for:
network.dnsCacheExpiration
and set its value to zero (0).
Windows
To clear the Windows DNS cache, open a Command Prompt window with administrative privileges. Type the following command and press Enter.
ipconfig /flushdns
macOS
On macOS, you should consider the version of macOS running on your computer:
macOS Yosemite and later
sudo killall -HUP mDNSResponder
macOS 10.10 – 10.10.3
sudo discoveryutil mdnsflushcache
After entering, you will need to enter your administrator password.
iOS
To clear the DNS cache on your iPhone or iPad, enable airplane mode for 10-15 seconds. You can do this from the Settings app.
If that doesn't resolve any issues, simply restart your device.
Android
Clear the DNS cache on Android via your browser. Open the Settings app and find Apps. In the list of installed apps, select the browser you are using. On the browser details page, you will see an entry for the amount of storage it is using. Tap it.
On the screen that shows you storage details, you will find a Clear Cache button. Tap it to clear the DNS cache.
