Is the following editor behavior a bug or intended behavior? Is there something I can do about it? I'm on Windows 10 Pro and am using Unity 2018.2.1f1 When I have two instances of Unity Editor open (two different projects). Let's call them instances A and B When instance A has the focus and I switch to instance B, then back again to A, all scripts of instance A get recompiled, even if absolutely no changes were made. At least I think it's all scripts that get recompiled. The reason I came to this conclusion is because I get the "Hold On - Recompiling scripts" dialog for about 15 seconds and I'm specifically working with assemblies to cut down on compilation time. When I just make some changes to a script in Visual Studio and go back to Unity, recompilation normally takes about 1-3 seconds. That's why I believe it's really recompiling everything. I can't imagine how else it could take this long. This also happens with indirect switches. E.g. If I alt+tab from instance A to Firefox, then to instance B, then to Firefox again and then back to instance A It doesn't happen if I just switch focus to anything that is not an Unity editor instance. For example, if I switch from instance A to Firefox/Visual Studio/etc and back again to A, nothing gets recompiled. I hope someone has a workaround or at least an explanation for this. Waiting 15 seconds isn't the end of the world but the project's only going to get bigger and it really starts to add up if you switch frequently. Thanks a lot and have a nice day!