How do I profile Vim startup time to find out which plugins are slowing it down?

Explanation

When Vim starts slowly, the --startuptime flag writes a timestamped log of every script and plugin loaded during initialization. Sorting by the second column (elapsed self-time) reveals the biggest offenders at a glance.

How it works

• --startuptime {file} tells Vim to write profiling data to {file} while loading
• Each line records three time columns: total elapsed, self (exclusive) time, and source file
• +qall opens Vim and immediately quits so you capture startup overhead without interactive use
• sort -k2 -rn sorts numerically in reverse by the self-time column so the slowest entries appear first
• head -20 shows only the top 20 worst offenders

Example

$ vim --startuptime /tmp/vim-startup.log +qall
$ sort -k2 -rn /tmp/vim-startup.log | head -5
  342.100  123.450  000.000: sourcing /usr/share/vim/autoload/slow_plugin.vim
   82.340   80.210  000.000: sourcing ~/.vim/pack/plugins/start/heavy.vim
   45.001   44.800  000.000: sourcing ~/.vim/plugin/legacy.vim

The second column is the time (in milliseconds) spent exclusively in that file. Files above ~30ms are worth investigating.

Tips

• For Neovim, the flag is the same: nvim --startuptime /tmp/nvim-startup.log +qall
• Run several times and compare results since cold-start I/O can skew numbers
• Consider lazy-loading plugins that appear near the top of the list
• :set loadplugins? can confirm whether plugins are even loading in a given context