Windows, macOS, and Linux store the IP addresses of the sites you visit in a special memory, the DNS cache. Sometimes this cache must be purged to resolve connection problems. Here's how to empty it.
When you surf the Web, you leave traces of your passage on the sites you visit. Your web browser also collects - with your consent - cookies in order to facilitate your navigation and subsequent visits to the sites you visit. If you do not want to keep this data, you can obviously clear the browser cache easily by consulting our practical sheet. However, web browsers aren't the only ones that keep data about your web activity. Operating systems such as Windows, macOS or Linux also record information, in particular within the DNS cache which stores, temporarily or not, data on the sites visited.
All servers hosting websites have their own IP address on the Internet (read our factsheet here to learn all about IP addresses). However, as it is not easy to remember a series of numbers (like 216.58.215.46), each IP address corresponds to a domain name (like google.com to which this IP address is attached). It is for this purpose that the DNS servers (for Domain Name System) were developed. They can be compared to a gigantic directory that maps the URLs of sites as you know them to their IP addresses on the network. All web browsers contact a DNS server to take you to the website you are requesting. And to speed up the process, the OS maintains a DNS cache in which the used - and valid - DNS of the websites visited are kept. Thus, when connecting to a website that you frequently visit, it is this cache that is used to speed up the connection.
Why purge the DNS cache?
Most of the time, the data stored in the cache contains information on the validity period of the DNS. After this defined duration, they are normally deleted from the cache. However, this "lifespan" can be very long. And for a malicious person using your browser, it would be easy to compile a list of your web habits by crawling this cache even if you regularly purge your browser's cache. In addition, in the event of a cyber attack on your PC or Mac, a hacker could easily change the address of a DNS server stored in the cache in order to redirect you to another site without you realizing it. Finally, the DNS cache can also be counterproductive. If a website changes address, the information stored in the cache will not allow you to access it and your browser will display an error message. By regularly purging your system's DNS cache (an operation called DNS Flush), you can start from a clean base. This is easily done, no matter what system you are using. It is recommended that you do this as soon as your browser directs you to an unusual site instead of the one you normally visit, or if you have connection problems on certain sites.
There is no specific application for this operation. To flush your system's DNS cache, you will need to use one or more command lines. Rest assured, you can copy and paste them to use them so as not to make any typing errors.
How to clear DNS cache in Windows 10?
To empty the DNS cache on a PC, the easiest way is to go through the classic command prompt or the PowerShell of In Windows 10.
- Right-click the button Start and choose Windows PowerShell.
- The command prompt is displayed. You can view the contents of the DNS cache by typing the command: ipconfig / displaydns and validate by Starter.
- To empty the cache, enter the command ipconfig / flushdns and validate by Starter.
- A text message then confirms that the cache has been purged.
How to clear DNS cache on Mac?
To empty the DNS cache in macOS, you must type a command on the keyboard via the Terminal. Nothing complicated, don't worry, even if you are not used to command lines!
- Open the folder Applications > Utilities and launch the application Port.
- In the window that appears, type the command sudo killall -HUP mDNSResponder; sudo killall mDNSResponderHelper; sudo dscacheutil -flushcache; say the macOS DNS cache has been flushed and validate by Starter.
- Your administrator password is then requested. Enter it. It does not appear during entry for confidentiality reasons. Validate by Starter.
- After a few seconds, an audio message informs you of the success of the operation.
How to clear the DNS cache with Linux?
Depending on the Linux distributions, the DNS cache can be saved in different ways. But in all cases, you must use the Terminal to purge it.
- Open the Port and enter the command corresponding to the application used.
- For pdnsd: sudo pdnsd-ctl empty-cache and validate by Starter.
- For dnsmasq, dns-clean or even ncsd: sudo /etc/init.d/dnsmasq restart ou sudo /etc/init.d/dns-clean restart ou sudo /etc/init.d/nscd restart and validate by Starter in order to restart the service.
DNS flush: how to flush DNS cache
Contents Why purge the DNS cache? Clear DNS cache on PC Clear DNS cache on Mac Clear DNS cache with Linux When you surf the Web, you leave traces of your passage on the sites you visit ....
