Add this to the start of your .zshrc file:

# zmodload zsh/zprof

then add this as the last line:

# zprof

and when you start your zsh session you’ll get a bunch of data on what’s making your startup slow.

For me it was nvm and it deciding what version to run, taking over 5 seconds to decide, when most of the time I don’t use or need nvm. I followed the advice from Aron Schueler over on hs blog and ended up with something like this, and a much faster startup time.

This is my “after” timing, I wasn’t going to write it up, I just Googled slow startup times for zsh and thought I’d write up what I found. Scott Spence also has some advice if your slowdowns don’t come from NVM.

Last login: Mon Jul 21 13:34:58 on ttys005
num  calls                time                       self            name
-----------------------------------------------------------------------------------
 1)   30         106.14     3.54   53.74%     66.24     2.21   33.54%  _omz_source
 2)    2          25.07    12.53   12.69%     25.07    12.53   12.69%  compaudit
 3)    1          19.24    19.24    9.74%     19.24    19.24    9.74%  (anon) [/Users/stuart.grimshaw/.oh-my-zsh/plugins/emoji/emoji.plugin.zsh:14]
 4)    1          35.30    35.30   17.87%     15.28    15.28    7.74%  spaceship::core::load_sections
 5)    1          35.61    35.61   18.03%     10.55    10.55    5.34%  compinit