How to Flush DNS on macOS: The Definitive Guide

So, you’re having trouble accessing a website, or maybe things are just running a little sluggish online? You suspect it might be a DNS issue? You’re on the right track. Flushing your DNS cache on your macOS system is often a quick and surprisingly effective solution. Here’s how you do it, plain and simple: the method depends on which version of macOS you’re running.

For macOS Ventura, Monterey, Big Sur, and Catalina:

1. Open Terminal. You can find it in /Applications/Utilities or by using Spotlight search (Command + Spacebar).

2. Type the following command and press Enter:

   sudo dscacheutil -flushcache; sudo killall -HUP mDNSResponder 

3. You will be prompted for your administrator password. Enter it and press Enter. Note that you won’t see any characters as you type your password – this is normal for security reasons.

That’s it! Your DNS cache should now be flushed.

For macOS Mojave and High Sierra:

1. Open Terminal (as above).

2. Type the following command and press Enter:

   sudo killall -HUP mDNSResponder 

3. Enter your administrator password when prompted.

For macOS Yosemite and El Capitan:

1. Open Terminal.

2. Type the following command and press Enter:

   sudo discoveryutil mdnsflushcache sudo discoveryutil udnsflushcaches 

3. Enter your administrator password when prompted.

For macOS Mavericks:

1. Open Terminal.

2. Type the following command and press Enter:

   sudo killall -HUP mDNSResponder 

3. Enter your administrator password when prompted.

For macOS Lion and Mountain Lion:

1. Open Terminal.

2. Type the following command and press Enter:

   sudo dscacheutil -flushcache sudo killall -HUP mDNSResponder 

3. Enter your administrator password when prompted.

Why the Version-Specific Commands?

The underlying mechanisms for DNS resolution and caching have evolved across different versions of macOS. Apple has used different tools and processes, hence the need for distinct commands. Using the wrong command for your operating system simply won’t work. So, make sure you use the one that is suited for your system.

Now that you know how to flush your DNS cache, let’s dive deeper with some frequently asked questions.

Frequently Asked Questions (FAQs)

1. What exactly is a DNS Cache?

Think of the DNS cache as your computer’s little address book for the internet. When you type a website address (like www.example.com), your computer needs to translate that into an IP address (like 192.0.2.1) so it knows where to find the website’s server. This translation is handled by Domain Name System (DNS) servers. Your computer stores these translations in its DNS cache so it doesn’t have to ask a DNS server every single time you visit the same website. This speeds things up considerably.

2. Why would I need to flush my DNS Cache?

Sometimes, the information stored in your DNS cache becomes outdated or corrupted. This can happen if a website’s IP address changes, or if there’s a problem with the DNS server your computer is using. Outdated or corrupted entries in the DNS cache can lead to various problems, including:

• Inability to access websites: You might see an error message like “Server not found” or “DNS server could not be found.”
• Accessing the wrong website: In rare cases, a corrupted DNS cache could direct you to a malicious website instead of the intended one.
• Slow browsing speeds: If your computer is constantly trying to use outdated DNS information, it can slow down your browsing experience.

3. How often should I flush my DNS Cache?

There’s no fixed schedule for flushing your DNS cache. You only need to do it when you suspect there’s a problem with DNS resolution. If you’re experiencing issues accessing websites or notice slow browsing speeds, flushing the DNS cache is a good troubleshooting step.

4. Will flushing my DNS Cache delete any important files?

No. Flushing the DNS cache only clears the stored list of website names and their corresponding IP addresses. It doesn’t delete any of your personal files, documents, or applications. It’s a safe and harmless operation.

5. Does flushing DNS affect my internet connection?

Flushing your DNS cache doesn’t directly affect your internet connection. However, it may cause a temporary slowdown in browsing speeds immediately after flushing, as your computer will need to re-resolve the IP addresses of the websites you visit. This slowdown is usually minimal and short-lived.

6. What is mDNSResponder and dscacheutil?

mDNSResponder is a process on macOS responsible for multicast DNS (mDNS) and DNS Service Discovery (DNS-SD). It helps your computer find other devices and services on your local network. The command killall -HUP mDNSResponder essentially restarts this process, forcing it to clear its cache. dscacheutil is a utility used to query and modify the Directory Service cache, which includes DNS information. The specific command used depends on the macOS version due to changes in how these utilities are implemented.

7. Why do I need to enter my administrator password?

The commands used to flush the DNS cache require administrator privileges because they modify system-level settings. Your administrator password is required to authorize these changes.

8. What if flushing the DNS Cache doesn’t fix my problem?

If flushing the DNS cache doesn’t resolve your issues, the problem might lie elsewhere. Here are some other things you can try:

• Restart your router: A simple reboot of your router can often resolve connectivity issues.
• Change your DNS servers: Try using public DNS servers like Google’s (8.8.8.8 and 8.8.4.4) or Cloudflare’s (1.1.1.1 and 1.0.0.1). You can change your DNS settings in your Network preferences.
• Check your internet connection: Make sure your internet connection is working properly. Try accessing websites from another device on your network.
• Contact your internet service provider (ISP): If you’re still having problems, there might be an issue with your ISP’s service.

9. How do I change my DNS servers on macOS?

1. Go to System Preferences > Network.
2. Select your active network connection (usually Wi-Fi or Ethernet) in the left sidebar.
3. Click Advanced…
4. Click the DNS tab.
5. Click the + button to add new DNS server addresses. Remove any existing addresses.
6. Enter the DNS server addresses you want to use (e.g., 8.8.8.8 and 8.8.4.4 for Google DNS).
7. Click OK.
8. Click Apply.

10. Is there a graphical user interface (GUI) way to flush DNS on macOS?

No, macOS doesn’t provide a built-in GUI for flushing the DNS cache. You must use the Terminal and enter the appropriate command. While some third-party applications might offer this functionality, it’s generally safer and more straightforward to use the built-in Terminal commands.

11. What’s the difference between DNS cache and browser cache?

The DNS cache stores IP addresses associated with domain names, whereas the browser cache stores website resources such as images, HTML, and CSS files. Clearing the browser cache aims to load web pages faster by storing these resources locally, reducing the need to download them repeatedly. Flushing the DNS cache focuses on resolving domain names to IP addresses correctly. They are separate caches that serve different purposes.

12. What if the terminal commands are not working?

First, ensure that you are typing the command exactly as shown, paying close attention to spaces and capitalization. The commands are case-sensitive. Second, double-check that you have selected the correct command for your macOS version. If the commands still fail, try restarting your Mac. A simple restart can resolve temporary glitches that might be preventing the commands from executing properly. Ensure also that you are logged into an account with administrator privileges.