It can be really frustrating if MacBook Keeps Disconnecting from WiFi. Fortunately, this annoying problem can be fixed using troubleshooting steps as provided below.
Mac Disconnecting from WiFi
In general, the problem of Mac frequently disconnecting from WiFi is related to Modem/Router going through problems, Expired DHCP Lease, Change or Corruption in Network Settings.
Another common reason for Mac Disconnecting from WiFi is due to the MacBook trying to connect to an inactive or weak WiFi Network, instead of connecting to your preferred WiFi Network.
This can happen, if you had previously connected to other WiFi Networks (Office, Library, Airport or others) and these Networks are saved on your Mac.
1. Power Cycle Modem/Router
Disconnect the Modem/Router from its Power Supply source > wait for 60 seconds and connect back the Modem/Router to its power supply source.
After this, you might be pleasantly surprised to see WiFi working without any interruption on your MacBook.
2. Renew DHCP Lease
Click on Apple Logo in top-menu bar and select System Preferences in the drop-down menu.
On the next screen, click on the Network icon.
On the next screen, select your WiFi Network in the left-pane. In the right-pane, scroll down and click on Advanced button.
On the next screen, switch to TCP/IP tab and click on Renew DHCP Lease button.
Finally, click on OK to save these revised DHCP Settings on your computer and close Network Settings screen.
3. Setup Network Priority
As mentioned above, the problem might be due to presence of multiple saved WiFi Networks on your MacBook. This issue can be fixed by setting up Network Priority on your MacBook.
Click on Apple Logo > System Preferences > Network. On the next screen, select WiFi in the left-pane. In the right-pane, scroll down a bit and click on the Advanced button.
On the next screen, drag your Preferred WiFi Network to the top in Preferred Networks window.
Click on OK to save your Preferred WiFi Network Settings.
Note: You can remove unwanted WiFi Networks from your MacBook by selecting the Network and clicking on the (-) Minus Icon.
4. Create New WiFi Network
Note down your WiFi Network Password and follow the next steps to Create a New WiFi Network on your MacBook.
Click on Apple Logo > System Preferences > Network. On the next screen, select your WiFi Network in left-pane, click on the (-) Minus icon and click on Apply to remove WiFi Network from your Mac.
On the same screen, make sure Automatic Location is selected and click on the (+) Icon.
On the pop-up, select Wi-Fi as the Interface, type a Name for the WiFi Network (Optional) and click on Create.
Click on Apply to save the New WiFi Network on your Mac. Switch ON the WiFi Network on your Mac and see if you are able to connect to Internet.
5. Try Wireless Diagnostic Tool
If above methods did not help, you can try the built-in Wireless Diagnostics tool as available on macOS and see if it comes up with any suggestions.
Open Spotlight Search (press Command + Space keys) > type Wireless Diagnostics in Spotlight search window and click on Wireless Diagnostics.App.
On the next screen, click on the Continue button and allow Wireless Diagnostic Tool to find problems on your device.
Note: The Wireless Diagnostics tool may temporarily change certain network settings on your computer.
6. Change DNS Servers
If you are frequently experiencing WiFi connectivity problems, the issue might be related to DNS server of your Internet Service Provider (ISP) being over-crowded or going through problems.
In such cases, switching to Google DNS or DNS Servers provided by Amazon or Open-DNS helps in fixing the problem.