Fix slow ZSH startup due to NVM

NVM can really be helpful when dealing with older projects. But there’s a problem, still. The nvm installation adds a portion of code to your .zshrc to enable autocompletion. This, in turn, slows the startup of your shell quite a lot.

But we can easily fix this slow zsh startup! Instead of always loading your nvm autocompletion, we can command oh-my-zsh to just load nvm ressources on-demand, also known as lazy-loading.

How do I check if just NVM slows my ZSH startup?

That’s easy. In your ~/.zshrc you can simply add zmodload zsh/zprof as first line and zprof as last line. This will prove you a nice output on which plugin caused what delay.

So go ahead, add these both lines to your shell startup script and time your shell startup with time zsh -i -c exit. This will start your ZSH and execute the exit command.
Scroll a bit up and your zsh output should blame nvm:

Bad, right? That’s almost 90% startup time caused by a single tool I
don’t use that much. So let’s fix this!

How do I fix the slow zsh startup?

As the average ZSH user, you probably already have different plugins provided by oh-my-zsh. If not, really, go ahead and get yourself some nice plugins! It’s a community driven aggregator of many many great plugins.

The plugin we need now is the nvm plugin. It’s already included in oh-my-zsh and should be activated in your plugins array somewhere in your .zshrc.

But you also want to add the line zstyle ':omz:plugins:nvm' lazy yes, which enables the
lazy-loading mode. This mode defers the load of the nvm plugin and activates the script when using it.
To further optimize your startup you can replace that line with zstyle ':omz:plugins:nvm' autoload yes.
This will only source the plugin in directories that contain a .nvmrc file. So, in conclusion,
add/modify the following in your zsh startup script:

zstyle ':omz:plugins:nvm' lazy yes
# Alternative:
# zstyle ':omz:plugins:nvm' autoload yes
plugins=(
  nvm
  // [...]
)
// [...]

Also, be sure to remove the lines added by nvm, they should be somewhere at the bottom of your script, mine looked like:

export NVM_DIR="$HOME/.nvm"

[ -s "$NVM_DIR/nvm.sh" ] && . "$NVM_DIR/nvm.sh"  # This loads nvm

[ -s "$NVM_DIR/bash_completion" ] && . "$NVM_DIR/bash_completion"  # This loads nvm bash_completion

Checking fixed startup times

Now, go to any directory that shouldn’t autostart nvm and check your timings again. Mine looked like this:

As you can see above, nvm support takes now much less time to start, while still being available “on-call”.

Done!

Now you can safely remove the debugging lines we introduced to our .zshrc earlier.

Hopefully I could help you a bit with this short post, see you around for the
next one 🙂