Fix Wi-Fi Problems With Mac OS Sierra

A Mac without Wi-Fi is a crippled Mac. With everything you do on your Mac having a good chance of being connected to something online, you probably want to fix your Sierra Wi-Fi problems pronto. Let’s get going with exactly just that.

Slow or dropped Wi-Fi connections with Mac OS Sierra?

If your Mac fails to reconnect to your Wi-Fi network after you wake it up or when you shuttle between two Wi-Fi networks that you commonly use, the fix is probably an easy one. The following fixes might also fix your Sierra slow problems as well, especially if your Mac is slowing down only when you need to do something online.

Before we get started, I always recommend that you use Time Machine to backup your Mac. Yes, it is not a fun process and is a bit cumbersome. But then, nobody wants a Mac that stares back at them blankly, like it hasn’t known you at all, even though you have shared so many of your memories and work with it.

So first, back up your Mac before you run the following fixes!

Fix 1 – Resetting your Wi-Fi connectivity preferences in Mac OS Sierra

  • Quit all applications or programs that are actively using the internet (browser, iTunes etc)
  • Turn off your Wi-Fi connection on your Mac
  • Enter /Library/Preferences/SystemConfiguration/ in the Finder window
  • Find the following four files
    • NetworkInterfaces.plist
    • preferences.plist
  • Copy these files onto a thumb drive or another folder on your Mac, just in case (Optional step but recommended, in case something goes wrong, you can paste them back)
  • After backing up the above files, delete these files in the location mentioned above
  • Restart your Mac
  • Restart your Wi-Fi router also for good measure, before your Mac restarts
  • Restarting your Mac will cause your Mac to rewrite these files, hopefully with corrections that will fix your Wi-Fi problems

Fix 2 – Creating a network connection with Custom DNS (Slightly Technical)

You might not understand all the jargon mentioned in this particular fix. But, it can help fix your Sierra Wi-Fi problems for good. Might be well worth a try if our first fix didn’t do it for you.

  • Quit all your internet using applications
  • Go to Apple Menu – System Preferences -> Wi-Fi -> Select your Wi-Fi connection -> Location -> Edit Locations -> + (Click on + to create new location)
  • Name your new Wi-Fi connection to any name that you want
  • Join the new Wi-Fi connection
  • Enter your Wi-Fi connection password when prompted
  • Once connected to your new connection, go to the advanced tab (bottom right)
  • Click on TCP/IP – > Renew DHCP Lease -> Apply -> DNS -> + (Lower left corner)
  • Enter the following DNS Server addresses in the white space that is given for DNS servers: (The following DNS addresses are Google’s DNS addresses. It is very safe to use)
  • Click OK. Then, click on the Hardware tab
  • Click Configure -> Manually -> Custom
  • Type in 1453 as MTU number
  • Click Ok
  • Click Apply to save and apply all your changes

If Fix 1 didn’t work, this Fix 2 should definitely fix your Sierra Wi-Fi problems. If this fix also doesn’t work, you can just go ahead and delete this new network connection that you created, if you fear that it might harm your Mac in any way. Not that it does any harm but it is pointless to have a network connection present when it just doesn’t work.

Other fixes you can carry out to fix your Mac OS Sierra problems

If you are the type that hasn’t restarted your Mac in a long, long time, instead only using sleep, a simple restart might fix your Wi-Fi problems. Besides trying to fix your Wi-Fi with this simple fix, it is also recommended that you restart your Mac from time to time, so updates and system resets apply, to help your Mac stay up to date in terms of performance.

You must also investigate if your modem or router is working properly. Bring a friend’s laptop and see if it connects to your Wi-Fi connection. Or, you can use your phone and tablet to connect to your Wi-Fi router. If no devices can connect to your Wi-Fi router, it is obviously a problem with your router and not your Mac’s Wi-Fi receiver.

In some cases, your Wi-Fi router might have two frequencies. There have been many occasions when only one band works (2.4 GHz or 5 GHz). If that is the case, use the frequency that works.

Other fixes that you can try are to run a PRAM and SMC reset, both Mac hardware resets that will not destroy any of your user data. They are soft resets that will rewrite some configuration files that might fix your Mac’s Wi-Fi problems and even help it speed up a little. In some cases, a PRAM reset or SMC reset might cause you to re-enter your date and time information but that’s about the only thing it will require you to do on your Mac.

13 thoughts on “Fix Wi-Fi Problems With Mac OS Sierra

  1. Helmar

    My issue is that it will not connect to an existing wifi anymore, whereas a connection from my MacMini and my Android phone is established without problems. The MBP – nothing!

    I have taken both steps 1 and 2, but to no avail. The MBP does connect to another wifi hotspot I set up on my Android, so technically it’s working, and the router, too (as evidenced by the other two devices), yet them MBP with Sierra on it – nothing? Any idea?

    1. elcapitan Post author

      Hello Helmar. Are you still have this issue? Please let us know. I am sorry I missed your comment earlier.

      1. Rich

        I am having the same issue as Helmar. My mac won’t connect to any existing Wi-Fi spots anymore. Any suggestions of what I could do?

  2. Longtime Apple Customer

    I’m sorry, but “Fix 1 – Resetting your Wi-Fi connectivity preferences in Mac OS Sierra” is basically the equivalent of:

    stand on your head
    speak the alphabet backwards

    Here’s a better solution:
    tell your PMs to slow their roll. don’t release a new OS until its stable, and ready for the masses.
    (i.e. not being able to connect to the internet after waking a computer from sleep = not stable, not ready)

    1. elcapitan Post author

      Offensive much? Please pass on your message to Apple directly, if you have such a strong grudge against them.

    2. Paul

      Considering the number of people (including myself) that solved the issue with that solution, I think that next time you should:
      – speak the alphabet backwards
      – lather
      – rinse
      – repeat
      before opening your mouth.

  3. Aziz

    My problem is that interntet connection just drops down randmoly and it only works again if I turned the Wi-Fi off and then turned it on! Can you think of other solution that might help me? And yes I have tried all the solutions above and I still have the same problem.

    Thank you

    1. elcapitan Post author

      Are you using a dual band Wi-Fi router? Sometimes, one band always results in dropped connections. You could try “forgetting” the problematic band and only make your Mac connect to the stable one. Hope that helps. Sorry but I don’t have anything else to offer at the moment.

  4. Alfredo Perez

    I cannot find any of those files in my mac. I do not have a SystemConfiguration folder. Any ideas? wow I am concerned now, my wifi drops a lot since I upgraded to Sierra


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