Today i started minecraft with the new update.
On the old version (1.15.2) i got around 120fps stable.
I created a new world on 1.16, and experienced huge fps drops. I now get around 40fps, and sometimes a little more. Sometimes a few seconds 120 fps, but that is not very often.
I contacted a friend about this and he experienced the same problem. We get around 1/3 of the fps we normally got in 1.15.2
Created a reddit post about this too: https://www.reddit.com/r/Minecraft/comments/hefvmz/huge_fps_drops_in_minecraft_java_edition_116/?utm_medium=android_app&utm_source=share
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Please read the moderator note on MC-187345 - we no longer track "my game is slower" issues if they are far too vague.