El Capitan Network Slowness

After using El Capitan for a while I noticed that my network activity was not very responsive. I have not read too much about this online, but for whatever reason I was not getting my normal network speeds. I found a fix in an old standby.


Initial Procedures

I did all the usual things when first investigating this problem. Initially, I restarted the modem and rebooted the iMac. When that did not work I ended up using this Flush DNS command in the Terminal app:

sudo dscacheutil -flushcache;sudo killall -HUP mDNSResponder;say flushed

The command worked. I then rebooted, but still no joy. Then, I decided to insert the OpenDNS address in my Network area. Sometimes using a different DNS setting can resolve slow network issues. But, that was not to be on this occasion. I also “Reset” Safari, but to no avail.

I could not decide if this was hardware or software related. I have a “test” user on my iMac for troubleshooting purposes so I logged out of my main account and logged into the “test” user account. Network activity was back to normal in the “test” account, so there must be something in my main account that is causing this issue.

Ultimate Solution

At this point I suspected it was some kind of problem in my account from the El Capitan upgrade. One of the best things you can do on a Mac is clear out cache files using a utility app. Even though I use the excellent CleanMyMac 3 I still occasionally use my old standy Onyx by Titanium Software for this purpose. There is a version of Onyx for every Mac operating system, but the El Capitan version had not been released yet. However, after checking online this morning it was there, so downloaded and installed it. Here is the new interface by the way:

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What I wanted to run was the “Cleaning” routines:

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Understand, I ran each one in turn, but instead of restarting like it suggests I just closed that routine and ran the next one. When I was done, then I restarted the Mac. The one that held the most promise was “Internet”, but it didn’t hurt to run them all.

After restarting my network speed was back!! And, the El Capitan install just seemed even snappier than before. There was probably some cache cludge between El Capitan and the previous Yosemite OS, but Onyx cleaned it all out.


Onyx is a great program, been using it for years. I am so glad they have continued their support into the El Capitan OS. If you are having network issues in El Capitan than I highly recommend using Onyx to clean your system up.