iMac 27'' 2017 5K not smooth


macrumors newbie
Original poster
Jul 23, 2014
South Africa
So I got a 2017 27'' iMac. The top spec model. I've noticed that animations on certain apps is very sluggish. Like when I maximize Firefox it's extremely sluggish. Youtube on Safari is not very snappy as it should. Feels like my 2015 MacBook is much more responsive.

The iMac is brand new and I even restarted with nothing running in the background and it keeps doing the same thing. The overall performance of the machine doesn't feel like it should. Not sure if I can run a benchmark to test things? Any suggestions?


macrumors 68030
Aug 20, 2015
That machine should be plenty fast and snappy. My iMac is several years older than yours and a few rungs down from "top spec" and everything generally works very smoothly and beautifully. I'm assuming that you have an SSD in there or at least a Fusion Drive? If somehow you had a plain spinning HDD, that alone could make it feel less responsive than your MacBook.

First thing I'd do is open up Activity Monitor to check the CPU usage and such, see if anything in the background is hogging resources. If the Mac is still super new, Spotlight could be still indexing (that process will show up as "mdworker" I believe) and that alone will slow things down for a while but the process should eventually finish its work and die down.

If you see nothing unusual in Activity Monitor, go to System Preferences → Users & Groups and set up a new, empty user account. Once that's done, switch over to it (skipping the Apple ID setup part) and then try stuff out there and see if it's any snappier. If that turns out to be the case, there may be some app or something in your main user account that is slowing things down.
Last edited:


macrumors 65816
Dec 24, 2007
If it really is "brand new" you'll find it's a bit on the busy side indexing for Spotlight for the first day or so. Hang in there.
  • Like
Reactions: Precursor

Cool Pup

macrumors 6502a
Jun 18, 2010
Dallas, TX
Probably the fault of High Sierra more than anything. I've noticed hangups and problems and compatibility issues with apps with High Sierra more than any previous form of the OS, I too have a 2017 iMac with high specs and notice some hiccups with the UI and applications. I'm just hoping the next form of OS will rectify these issues because I would much, much rather be on Sierra.
Register on MacRumors! This sidebar will go away, and you'll see fewer ads.