Step 1: Open Network Settings
Click the Apple menu → System Settings (or System Preferences).
Select Network.
Choose your active connection (Wi-Fi or Ethernet).
Step 2: Change DNS Servers
Click Details (or Advanced… on older versions).
Open the DNS tab.
Click + to add new servers:
Google:
8.8.8.8,8.8.4.4Cloudflare:
1.1.1.1,1.0.0.1
Remove old entries with –, then click OK → Apply.
Your Mac will now use the new DNS servers.
Step 3 (Optional): Flush DNS Cache
Open Terminal.
Run:
sudo dscacheutil -flushcache; sudo killall -HUP mDNSResponder
Enter your password if prompted.