I will be speedrunning 1.16.1. I dont have 2 monitors only 1 so therefore i cant use a timer and playing on windowed mode feels wierd, can i use a timer on my phone? Also if i do how do i calculate IGT? or do you do it im not sure. Thanks

i belive you only can see your timer if you have minecraft opened in not fullscreen or if you stream you can go to your stream on your phone and see the timer and chat if you have set that up

ok i see but can i still use a timer on my phone?

yes

If you still want to play Minecraft and see your timer on one monitor/screen, you can make Minecraft borderless windowed mode and go fullscreen from there. Download ThatFlashCat's "BorderlessMinecraft" program or find another one, it's the one I use for streaming and speedrunning Minecraft on a laptop.

Also for IGT, look at Resources and choose one of the timers shown there. I chose Kohru's Livesplit extension for my IGT but all of them should be good to use.

Good luck on speedrunning :)