It can be really frustrating if your Mac Keeps Disconnecting from WiFi Network. Fortunately, this annoying problem can be fixed using troubleshooting steps as provided below.
Mac Frequently Disconnecting from WiFi
In many cases, the problem of WiFi frequently disconnecting from Mac occurs due to Modem or Router going through problems, change in Network Settings or due to expired DHCP Lease.
Another reason for Mac Disconnecting from WiFi or not at all connecting to WiFi is due to Mac trying to connect to a weaker or inactive WiFi Network, instead of connecting to your preferred WiFi Network.
This can happen, if you had previously connected your MacBook to other WiFi Networks (Office, Library, Airport or others) and these Networks are saved on your Mac.
1. Power Cycle Modem/Router
Before going through other troubleshooting steps, make sure that the problem is not due to your Router/Modem going through temporary technical glitches.
Simply, switch OFF the Power Supply to your Modem/Router > 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, 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.
Click on OK to save the 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. If this is the case, you need to setup 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
Before removing your current WiFi Network make sure that you note down your WiFi Network Password as you may be prompted to enter Password when you join New WiFi Network.
Click on WiFi Icon located in top-menu bar (top-right corner) and Switch OFF WiFi Network on your Mac.
Click on Apple Logo in top-menu bar > select System Preferences in the drop-down menu and click on 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 your MacBook 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 a case, switching to Google DNS or DNS Servers provided by Amazon or Open-DNS might help in fixing the problem.