How do I load a plugin on demand using Vim's native package system?

Explanation

Vim 8+ and Neovim have a built-in package manager. Plugins placed in pack/*/opt/ directories are not loaded automatically at startup — you control when they load by calling :packadd {name}. This gives you lazy-loading without any external plugin manager.

How it works

• Start plugins (pack/*/start/) — loaded automatically at startup
• Optional plugins (pack/*/opt/) — loaded only when you call :packadd {name} where {name} is the plugin's directory name
• Vim searches all pack/*/opt/ directories in your packpath (usually ~/.vim/pack/ or ~/.config/nvim/pack/)
• :packadd! (with bang) loads the plugin without running its plugin/ scripts — useful when sourcing vimrc at startup

Example

Directory layout:

~/.vim/pack/tools/opt/matchit/

Load it on demand:

:packadd matchit

Or load it conditionally in your vimrc only for certain filetypes:

augroup go_plugins
  autocmd!
  autocmd FileType go packadd vim-go
augroup END

Tips

• :packloadall forces all opt packages to load immediately — useful for debugging or one-off loading
• :packadd is idempotent — calling it twice on an already-loaded package is safe
• Prefer pack/*/opt/ for large or rarely-used plugins to keep startup time low
• The matchit plugin (extended % matching) ships with Vim itself in pack/dist/opt/matchit — enable it with :packadd matchit