Update: actually even when I set all my asset group to be uncompressed, sometimes randomly it would take up to 2 min to load the first asset, when it's doing that the game seems to be just sitting there with very low CPU usage and low Disk usage, like 8 mb/s, then after 30 second it would just to 90 mb/s, and at it for a while before it will finish loading.... really need help, it's blocking my clients with this issue. Update: I didn't call InitializeAsync, this me try look into that. Update: InitializeAsync handle doesn't seem to report value in PercentageComplete, this is a problem, especially when InitializeAsync can take a while. Update: so InitializeAsync finished really fast, so I still can't fingure out why it's so slow in standand alone build but never slow in editor pack mode, I tried set Application.backgroundLoadingPriority = ThreadPriority.High; but still extream slow, takes 2-5 min seems like the game just not doing anything except very low harddrive reads and framerate is very high and after 2-5 min the game suddenly loads, I can't get any percentage value working during this time. my standalone build is il2cpp could it be the issue? Also I am getting lots of random Could not produce class with ID 1108. when running il2cpp standalone build with addressable, I deleted library many time, and this still happens. Update: I think I finally figured out, my Async Upload Time Slice and Async Upload Buffer Size was too small. it was at 2ms and 4mb, changed to bigger value, finger crossed... Update: still same slowness no matter what I do, I think it's a disk seeks issue, but I can't find any information on how to pack the data in a more optimal way, also I can't separate into smaller asset pack due to a bug in addressable that is not fixed in 2019.2. Update: sorry this becomes like a blog, but now I learned what really happens is my asset dependency are all over the place, and it's basically trying to read all the file at the same time, and sometimes it's fast because it's cached by memory or windows cache. so what I really need to do is take a closer look at packing the only thing I want to load at a time.