XCode 10 simulator slow

Since upgrading to XCode 10 my iOS simulators have become really slow. There's a lot of lag when scrolling in tableviews or scrollviews. Is anyone else having this problem?


I got the same problem but it work fine on another mac. Don't know why !!!

I can't work ! please Apple make some fix.

My simulators have also slowed down by a large degree.

I noticed that the XR sumulator is faster than the 8 plus one. Still slow but at least usable.

I remember the time, many, many years ago, when the iOS simulators were actually extremely light, fast and efficient. They could simulate in real-time, full 60fps, even on slower Macs.

With every new version of Xcode, the simulators have become increasing slower. By this point they have become so slow that they are almost unusable. The Xcode 9 simulators were already really slow (running at about 10 fps on this iMac), but now with Xcode 10 they have become even slower. In fact, it's worse now because with Xcode 9 they were slow, but at least the framerate was quite steady and consistent. With Xcode 10 there framerate will fluctuate, between about 10 fps and something like 2 fps, at random intervals, making it almost unusuable.

This is even worse than ever before because now the simulator hogs 100% of CPU time, making everything in the operating system lag while the simulator is running. I can't do anything else at the same time.

Luckily this is probably the last iOS project I ever have to do with Xcode.

II noticed a strong deterioration in the speed of execution of the simulator, now I'm working on the physical device because otherwise I can not work.

If numbers matter, I'd like to add my complaint to this issue.

Especially slow are Tableview scrolling in pop-overs,

slide across screens and pop-up views - with a lot of transparency.

Using UIKit, Foundation, Core Graphics, MessageUI, and

WebKit.frameworks since iOS12 deprecated UIWebView.

The App has dozens of Cocoa Gesture Recognisers and many Pop-Overs.

All worked fine when build for 10.3 targets - simulators often faster + smoother than physical device animation.

Also previous Xcode environments allowed us to configure simulators for various fallback iOS versions - I think.

whereas now there is no fallback from 12.0 - is this true?

Also note build has gone from 20 modules to 200 tasks, huh? (Objc & Swift4.2 mix)

Thanks in advance

You can install older simulators from the menu Xcode > Preferences... > Components. (You might need to restart Xcode for it to notice the new simulator.)

Thanks for the tip Warp. Rolled back to 11.4 for maybe 50% improvement. Still a bit hesitant and jerky. May need to roll back further until12.1 or 2 comes along. At 2GB per simulator its annoying, as they were all downloaded before and existing on my machine before 12.0 update.

Other co-existing suspects.

* had a PUP (Mac Mechanic) on system - now gone I think?

* there has been a Java update recently?

* my mouse is intermittantly disconnecting. Reonnects on demand, but a new and bothersome symptom for a system which should have matured with robustness & reliability & some certainty after this many years. Apple's appetite for unwarranted change & deprecation irks me.

Simulators have become ridiculously slow. Timing any kind of transition or animation is impossible. I have tried every solution so far from changing FramebufferRendererHint to reinstalling simulators. I am about ready to go back to Microsoft world. Yesterday (xcode 9.xx) I was productive, today (Xcode 10) I cannot even get any work done. Absolutely insane. This is not a beta version either, This is the production version.

Slow to the point of being unusable. Yesterday, I was getting things accomplished. Today, I'm listening to my fans going into meltdown mode while the cursor slowly jumps across the screen.

I saw people had complaints about this in Beta but apparently they decided to release without fixing it, noting that there might be problems, or even acknowledging the issue.

Experiencing the same issue here, especially from running Xcode 10.0 on macOS Mojave 10.14 Beta.

Currently installing the GM version of macOS Mojave 10.14 so let's see if that resolves some of my issues.

Also contemplating installing Xcode 10.1 Beta since the Release Noteshave some fixes for bugs from the previous version, nothing detailing the level of slowness for the Simulators though.

I've encountered a lot more issues using iOS 12.0 Simulators. Anything iOS 11 and below seems to work okay, just not as fast as anything on Xcode 9.4.1.

I got the same problem

Fixed my issue by installing Xcode 9.2 on macOS Mojave Version 10.14

Don't think Xcode 10 is ready to be all that usable right now (at least for me and for those who have been having a lag with their Xcode Simulators).

One thing that did help for sure was deleting Xcode 10 altogether, installing Xcode 9.2 as well as its respective command line tools:

xcode-select --install

I also attempted to use Xcode 9.3.1 and still experienced issues with the Simulator (iOS 11 versions only) seemingly continue to lag behind the same way Xcode 10.0 did.

Hope this provides some sort of solace for anyone experiencing this issue on macOS Mojave.

Haven't bothered to try Xcode 10 Beta 1 just yet as I'm sure the Simulator issues are twice as worse. Seems like Xcode 9.2 will just have to do for now in my case...

If you'd like, try to measure the compile times on Xcode by copying and pasting the following in your machine's terminal:

defaults write com.apple.dt.Xcode ShowBuildOperationDuration -bool YES

The above has also helped me to gauge how optimized my builds were or if they were laggy at all for any reason.

same issue, **** slow...

I ended up downloading Xcode 10.1 Beta & macOS Mojave 10.14.1 Beta which definitely improved performance and speed on my Simulators.

Things seem to be in working order now and I don't have to result to using Xcode 9.2 (although I'll continue to use it on my other machine running High Sierra should I encounter any issues with this 10.1).

For the time being, I will continue to document any issues should I encounter any but I am definitely pleased with the patch Apple provided for macOS Mojave 10.14.1 Beta which seems to work marvelously in conjunction with Xcode 10.1.

Also, macOS Mojave 10.14.1 Beta has Group Facetime as a feature, so that's been really interesting to see. The Release Notes don't seem to have it documented for some reason..But Apple Insider casually mentions italong with other things that I'd expect to see in the Release Notes from Apple.

So improvements I've noticed:

  • Indexing is faster
  • Simulators don't take forever to boot, even upon initial use.
  • Not as much lag as opposed to Xcode 10.0 GM
  • Load times are generally faster but not by much

Overrall, keep your expectations low and hope for a GM fix soon.

Same **** here. MacBook Pro 17" Core i7, 4 physical cores + 4 logical, 16Gb RAM, 1Tb SSHD and **** simulator with 4-6fps