Compiling C# files in an otherwise empty project takes about 3 times longer in Unity 2019.3 than in Unity 4.6. Please see the provided videos. Spoiler: Video Creating C# script Spoiler: Video Deleting C# script Reproduce Create new project Right-click in Project window and chose "Create C# Script" Observe gears icon in lower right corner as indication when Unity is done Repeat these steps with Unity 4.6 and Unity 2019.3 Actual Creating and Deleting, probably recompiling in general, C# source files in Unity 2019.3 is significantly slower than in previous Unity releases. In my test: Unity 4.6 = 2 seconds Unity 2019.3 = 6 seconds Expected Newer Unity versions should not be slower than older ones. Note Please use hardware similar to the PC I used to submit the bug-report with. It probably can't be reproduced on high-end machines.