I have been trying to use ue4 on my mac for days and it had either been running really slow and causing my mac to run slow or in some cases, ue4 crashes and sometimes even my entire computer crashes. I understand it is not recommended to uses ue4 on mac but I only have access to a Mac.
My specs are:
Processor: 2.3 GHz Intel Core i5
Memory: 8 GB 2133 MHz
Graphics: Intel Iris Plus Graphics 655 1536 MB (Retina Display)
I am only able to reach about 10 FPS
The same for me with 16 GB ram and i7 3.1GHz cpu, also the same for another macbook with discrete graphics. It seems it’s something wrong with UE4 specifically for macOS 
I have an i7 Mac, 16Gb ram and dedicated GPU and it’s still pretty ■■■■slow. This video kind of explains the reason: Why Unreal Editor feels slow on a Mac - YouTube
Unfortunatly there is not a lot you can do. You can scale down the settings, turn off realitime etc but it is still quite a slow experience.
Having said that, I’ve never experienced a crash on UE4 on my mac (unless it was my fault with bad code), so there might be something else going on in your project.
It’s no secret that OSX isn’t really the right platform for performant games. Yes, I can play some games quite happily but there are limits. When it comes to UE4, playing as standalone does perform better than PIE but it does depend what you’re making. A simple game can run at 60fps quite happily but as soon as you throw in some complex shaders and dynamic lighting, the FPS drops quick.
In the case of the editor though, you’re experiencing further slow downs simply because of the refresh of multiple panels (which I’m sure has a CPU cost as well as GPU). In a stand-alone game, you’re only really refersing the game but in the editor, your refreshing the game, and the various editor panels.
That’s interesting though it’s not really the reason. Even when a game is running outside of the editor (e.g. stand-alone mode), it’s running much slower than it should. And it’s no doubt a 3d game with camera movements and so on will have to update all the screen every frame.
That’s not true about macOS, there are a lot of relatively heavy games running on macOS easily. Also it’s exactly about a simple game, didn’t get more than 20-30 fps even for the sample projects (e.g. Third Person example).
I’m running UE4.26 on a MacBook Pro 16" 2019 32gb RAM, AMD Radeon Pro 5300M 4 GB, Intel UHD Graphics 630 1536 MB. Irrespective of how powerful the machine is, I could only squeeze out 20fps while editing, and 30fps in PIE, running the very basic Animation project. I found out using Quarz Debug, that the whole editor refreshes every time even when idle but in focus. Unfortunately, I guess the Editor was build like that.
But here’s my fix for the general poor performance:** Editor Preferences > Plugins > Graphics Switching. Set “Renderer ID” to always use Dedicated Graphics**. In my case " AMD Radeon Pro 5300". Turns out that even with automatic graphics switched ON by default, it still performs poorly. You can optionally enable “Show Editor GPU Selector” to see which GPU is active while editing.
In conclusion, after setting to always use Dedicated Graphics, I now get 120fps (I couldn’t believe it at first) almost every time, except when I had StaticMesh and Animation Tabs open in the background There’s a significant drop in FPS when you have many tabs open. Strangely, UE4 editor keeps rendering all tabs even if you’re only focused on the Map Tab. So with every extra tab, an overhead is added. Close tabs you don’t need.
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