Fix Wi-Fi Problems in macOS Sierra

Some Mac users are reporting wi-fi difficulties after updating to macOS Sierra 10.12. The most common wireless networking problems seem to be either randomly dropping wi-fi connections after updating to macOS Sierra, or an unusually slow or delayed wi-fi experience after updating a Mac to Sierra 10.12.

We’ll walk through some some-tested troubleshooting steps to resolve wireless networking troubles with a Mac running macOS Sierra. 

What we’re going to cover here involves a longstanding approach to resolve most common wi-fi issues with Mac OS, composing primarily of removing existing wi-fi settings and then recreating a new network profile with some custom settings. These steps should resolve the most typical manifestations of wi-fi networking problems seen with macOS Sierra, which are the following:

• The Mac disconnects from wi-fi when wakes from sleep
• macOS Sierra drops wi-fi connections or disconnects from wireless at random
• Wi-Fi connections are unusually slow or have a higher ping than usual after updating to macOS Sierra

The approach may fix other networking related issues as well, but those are the primary wifi problems aimed to be addressed by this walkthrough. We’ll also cover some additional generic wi-fi troubleshooting tips that may be helpful if the primary two approaches do not resolve the difficulty. 

It is recommended to backup your Mac before beginning any of this process. Time Machine makes it easy, but you can use whatever backup method you’d like. 

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. Quit any active applications that are using wi-fi or the internet (Safari, Chrome, etc)
2. Turn OFF wi-fi by selecting the wi-fi menu bar item and choosing “Turn Wi-Fi Off”
3. Open Finder in macOS and pull down the “Go” menu and choose “Go To Folder” (or hit Command+Shift+G to get there quickly)
4. Enter the following path exactly into “Go to folder” window and choose “Go”
5. Locate and select the following files in the SystemConfiguration folder
6. 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 
7. 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”
8. 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 

1. Pull down the  Apple menu and choose “System Preferences”, then select “Network”
2. Choose Wi-Fi from the left list in the Network panel
3. Pull down the “Location” menu and select “Edit Locations”
4. Click on the [+] plus button to create a new network location with an obvious name like “Custom WiFi Fix”
5. Use the Network Name dropdown menu and select the wi-fi network you want to connect to
6. Now choose the “Advanced” button in the corner of the Network panel
7. Go to the “TCP/ IP” tab and choose “Renew DHCP Lease”
8. Now go the “DNS” tab, and under the “DNS Servers” list section click on the [+] plus button, adding each IP onto it’s own entry: 8.8.8.8 and 8.8.4.4 – these are Google Public DNS servers that are free to use by anyone but you can pick different custom DNS if you’d prefer
9. Now select the “Hardware” tab and set the ‘Configure’ option to “Manually”, then adjust the “MTU” option to “Custom” and number to “1453”
10. 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. 

3: Still Having Wi-Fi Trouble? Here Are More Troubleshooting Tips

If you’re still having trouble with wi-fi in macOS Sierra 10.12 or newer, you can try the following additional troubleshooting steps:

• Are you certain you are on the macOS Sierra final public release? The first GM seed was different from the final version (build 16A323), but you can download macOS Sierra again from the Mac App Store if need be and update to the final version
• Reboot the Mac into Safe Mode by rebooting and holding down the SHIFT key, when booted into safe mode, reboot again as usual – this is a process which dumps caches and can fix some finicky basic trouble
• Reset SMC on the Mac – requires a reboot and power cable
• Reset PRAM / NVRAM on the Mac – requires a reboot
• Power cycle the wi-fi router (disconnect it from power for 30 seconds or more, then turn it back on)
• Update the Wi-Fi router firmware if any update is available
• Avoid 5 GHz G and B networks if possible, aim to join a 2.4 GHz network N if one is available for faster speeds
• Temporarily disconnect Bluetooth and see if wi-fi works while Bluetooth is disconnected
• If all else fails, consider downgrading macOS Sierra back to El Capitan using Time Machine
• Still having wi-fi difficulties? Consider visiting an Apple Store or contacting official Apple Support

Have you experienced any wi-fi issues with MacOS Sierra? Does wi-fi drop or appear slower than usual for you after updating to macOS Sierra? Did the troubleshooting steps above fix the problem you experienced? Let us know your experience in the comments below.

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