Entering Play mode is suddenly extremely slow

Unity version 2018.3.1f1

Seemingly out of nowhere it now takes over a minute to enter Play mode. Looking at the profiler, it seems that “Prefabs.SavePrefab” is the main culprit, so I assume it’s something to do with prefabs.

My Canvas is a prefab with all of my various UI prefabs nested, but that’s pretty much the only significant prefab, everything else is generated at runtime. Does anyone have any insight as to what’s causing this, or have any suggestions for potential fixes?


Same here. Though I have to add, its seems no to be caused by switching to play mode itself but when the scene gets saved. I use an “autosave on switch to playmode script” which causes the same problem each time I press the play button.

Tested Unity Versions: 2018.3.0f2, 2018.3.1f1, 2018.3.2f1

I got a similar issue as described here, submitted a bug report: https://forum.unity.com/threads/performance-when-saving-prefabs.597514/