WiFi Issues After macOS Sierra 10.12.6 Update

Ever since I did the latest macOS Sierra Update, I've been having horrible wifi connectivity, the speed just keeps dropping sometimes to decimals. I've done everything to help including a custom wifi network, and resetting PRAM. Can someone help me solve this problem? Please help!

This is what I've done so far. And reset PRAM, and the obvious like cycling the router.

1: Remove Existing Wi-Fi Preferences in macOS Sierra

This is going to involve removing some system configuration files, therefore you should backup your Mac first, just in case. Do not remove any other system configuration files.

/Library/Preferences/SystemConfiguration/

com.apple.airport.preferences.plist
com.apple.network.eapolclient.configuration.plist
com.apple.wifi.message-tracer.plist
NetworkInterfaces.plist
preferences.plist

1. Remove those matching files, you can either place them into a folder on the desktop as a rudimentary backup, place them into the Trash without emptying, or actually delete them
2. After those matching wi-fi configuration files are out of the SystemConfiguration folder, reboot the Mac by going to the  Apple menu and choosing “Restart”
3. When the Mac has booted back up as usual, go back to the Wi-Fi menu and choose “Turn Wi-Fi On” and join your typical wireless network

When the Mac boots back up and wi-fi is enabled again, for many users their wireless internet connection will immediately work again as expected. If that’s the case, be satisfied with the relatively easy troubleshooting process and you don’t need to proceed any further.It’s often a good idea to reboot the wi-fi router the Mac is connecting to as well, which can resolve some simpler wi-fi router issues that sometimes pop up with certain router brands and Macs. This is easiest in a home environment where you can just unplug the router, let it sit for a minute or so, then plug it back in again. Obviously for a work or school computing environment that may not be possible though.Is your wi-fi working? Great, then you don’t need to do anything else. But what if your wi-fi is still dropping, still slow, still losing a wi-fi connection randomly when waking from sleep or for no apparent reason? Read on for more troubleshooting tips.

2: Set a New Network Location with Custom MTU and DNS

Assuming you’ve already removed the wi-fi preference files in the first major troubleshooting section above and wi-fi is still problematic with mac OS Sierra, you can proceed

Now click on “OK” and then click on “Apply” to set the network changes

Exit out of System Preferences and open an app that uses the internet like Safari, your wi-fi should work great now.

This troubleshooting method of specifying DNS (and, importantly, using known to be working DNS) with a lower custom MTU setting of 1453 is time tested and has routinely worked for resolving some of the most stubborn wi-fi networking problems in macOS Sierra and going further back to many prior Mac OS X releases too, each of which is often accompanied by some limited examples of wireless networking difficulties.