Compliling Unreal Editor and Game with Clang on Windows

Development Pipeline & Plugins
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Steps to Reproduce
Hi Epic Support,

I was curious about using Clang CL for compiling Unreal engine on Windows, both in game and editor configuration. We are experimenting with it and are curious what performance you can get out of it, in particular with ThinLTO enabled vs MSVC LTCG.

Would you recommend using it for Game builds or also for Editor builds? It would be nice for us to stick the same compiler throughout our builds.

Thanks in advance for your reply!

-Alessandro

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Hi,

We are supporting both compilers, MSVS and Clang. Depending on your game, you might have better results with one of them. Internally, people reported faster compile time, faster link time and faster execution with Clang 18 and Clang 20. I found report saying that Clang 19 had some regression. I also found reports that Clang with ThinLTO was slower to link and consumed more memory, you will have to try and measure. As far as I’m aware, we are shipping Win64 Fortnite client compiled with Clang because the compiled code was faster. If I remember well, we had to pay a little runtime memory increase though. The best I can recommend is to measure and find out what is best for you.

Regards,

Patrick

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