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?

Post marked as unsolved Up vote post of rodskagg Down vote post of rodskagg

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me too the simulator is super slow with any device I like to simulate the iPad Pro but it is super slow

I would like to share my knowledge with simulator performance issue. I have hybrid HTML5 + JavaScript app (web/android/iOS) and for android/iOS mobile apps I use web-view. I detected that some part of my app is extremely slow in Xcode simulator. It is part with Date object manipulations. When I run e.g. this simple JavaScript code

var x = new Date();

in cycle with e.g. 1000 iterations it runs fast (several tens milliseconds e.g. 30 ms) in any browser any device any platform including very old iOS device e.g. iPhone 5C and several years old iPad 2, BUT IN SIMULATOR IT TAKES 6000 ms (yes, 6 seconds!). So simulator is 200 times slower! Terrible! Jsfiddle demo here: https://jsfiddle.net/kjms16cw/ I see in Xcode console error: "[IPC] Connection::waitForSyncReply: Timed-out while waiting for reply". Interesting is that Xcode during that 6 seconds show app CPU usage 0% but in host device (MacBook Pro) monitor I see that CPU increased from about 5% before to 50% during test. Dear Apple can you explain please that low simulator performance? So Im not possible to test my app in simulator at all... we also need simulator for testing but also for creating screenshots for several resolutions required before app publishing in app store. My app is for public transport and we need to do lot of date calculations each second (several hundreds) which usually takes 10 ms but in simulator several seconds and interval each second makes app totally unresponsive and unusable in simulator.

I think the point is that you are not going upgrade your 2011 MacBook Pro. You are going to replace it.

Can you elaborate? I’m trying to decide what Mac to upgrade my 2011 MacBook Pro to and would like to make sure whatever I choose actually works. My MacBook is pretty much useless using the simulators.

The core issue here is that older versions of the simulator use the CPU for rendering. iOS 13 running on Catalina will utilize the GPU through Metal. You should have a much better experience with this year's releases.

Maybe you have put your debug in slowly animation.

Go to: Debug > Slow Animations


Try this ⌘T

I realize this is a late response, but I ran into this issue today and after searching on stackoverflow, I found that I had inadvertently pressed command+T, which triggers the "Slow Animations" (under the Debug menu in simulator). Pressing command+T again (or unselecting it in the menu) fixed the problem!

(I have option+command+T set to be a keyboard shortcut for the simulator's Hardware->Touch ID->Matching Touch command, I missed the option key and just hit the command+T accidentally, it didn't log in to my app, so pressed option+command+T again, then logged in and everything was sooooo.... slooooowwwwwww....... I thought some of the new code I added to the app caused a major problem, but removing it didn't help—it didn't dawn on me that I had hit command+T accidentally prior to this happening, then I found the stackoverflow answer, unchecked "Slow Animations" from the Debug menu, and all is back to normal!) Hope it's this simple fix for others who run into this issue.

This is happening to me too.

I have up to date Mojave, XCode & Simulator. This is on MBP 2018. Everything is new and the simular is unusable.

My laptop sounds like its going to take off when I spin up the simulator. Before XCode 10 I never had an issue.

I've disabled dark mode and its still the same.

Even using the simulator stand-alone without XCode its unusable. I click on Safari and it often misinterprets the click and thinks I've held it for a long press.

Is the common factor "slightly older MacBook Pro"? That's what I've got, and the simulators are totally unusable. They are, oddly, somewhat better if Slow Animations are turned on, though then of course the simulation is not so realistic and everything takes longer.

I have the same issue... and I've been having it since Xcode 9 actually... I quickly decided to try the 10 beta hoping it was fixed.

But nope - I have all the latest updates to Mojave and Xcode and the Simulator most of the time is unusanle. It takes multiple clicks (like 10-20) to perform an action like touch, and then it takes a few seconds to do the action. I don't know how to fix it 😟 - reminds me of Windows.

This is on a 2017 13" MBP

Although Xcode 10 is installable from High Sierra, it is not optimally compatible with that macOS version. Try macOS Mojave instead.

This has helped me in getting more performance improvements out of Xcode 10 but I just want to forewarn you all that I'm running macOS Mojave 10.14.1 beta 5 and Xcode 10.1 beta 3.

If those technical specs are not applicable to you, kindly disregard the following next steps I'll be presenting to squeeze more speed, optimal performance and efficiency out of your iOS Simulators running iOS 12 and above.

The reason why I specify these specs is because I've been downloading every single beta release since Mojave first came out and have been closely following each sequential release as a means of tracking which bugs have been addressed or fixed and if any beta release actually provides more optimal performance to my machine.

In this case, since we're discussing Xcode 10, let's begin:

  • First order of business: get rid of Dark Mode altogether, you don't need it as much as you think you do. It's gimmicky and actually slows down your performance on Xcode in every shape and form. Notice that weird lag when you're trying to get your iOS Simulator going while simultaneouly browsing Chrome? That has definitely been attributed to Dark Mode in my case and I have seen a substancial difference in performance when running my apps on the Simulator.
  • Turn off your device bezels by doing the following: Simulator > Window > Show Device Bezels (uncheck it if it checked by default).
  • If you haven't already, be sure that you're slowing your animations: Simulator > Debug > Slow Animations
  • Also, we're going to minize the quality of our graphics by doing the following: Simulator > Debug > Graphics Quality Override > Low Quality (although Device Default works just as well, quite frankly. There is no literal difference graphically between Low Quality and Device Default. They both present themselves quite similarly).

Since applying the following changes to my Simulator preferences, indexing takes less effort out of Xcode, launching the Simulator itself is almost instananeous and app installation happens in seconds. While it's not the record speed that I'm used to from Xcode 7.3.1 or even Xcode 9.2, it makes version Xcode 10 a lot more usable than before I implemented some changes on machine settings.

Again, I haven't tested any of these changes on Xcode 10 GM so this could potentially help just about anyone even if they're not running macOS Mojave beta or even Xcode 10 beta versions. I simply wanted to emphasize that my machine could be different than yours in the aspect that I'm running beta software so implement these relatively harmless changes at your own discretion.

Same issue here with Xcode 10, High Sierra 10.13.6, Macbook Pro i7 with SSD

The simulator is unusable.

I had the same problem with very slow simulator behavior on my Mac Pro 5.1 with XCode 10 (12 cores, 128GB RAM); simulator performance is fine on my Macbook Pro using XCode 10

In order to upgrade to Mojave I swapped to a metal-capabile GPU (supplied a few years ago by a well-known ******* based in Hollywood) and that solved the problem (well, either the graphics card or the Mojave upgrade did)

When using macos 10.13.6 and xcode 10 on mac pro 5.1, starting the simulator it's getting so slow and lagging, that you cannot work. Also entire system is getting slow. Rolling back to xcode 9 woun't help. Only time machine helps. Rolled back to 10.13.4 and xcode 9. Tried xcode 10.1 beta, the problem still exists. Can't update this mac to Mohave because of Apple requires only cards with metall support((