How do I change the cursor shape for different Vim modes in the terminal?

Explanation

Modern terminals support cursor shape changes via escape sequences. You can configure Vim to use a block cursor in normal mode, a thin line in insert mode, and an underline in replace mode — providing instant visual feedback about which mode you're in.

How it works

• t_SI — escape sequence sent when entering Insert mode (Start Insert)
• t_EI — escape sequence sent when leaving Insert mode (End Insert)
• t_SR — escape sequence sent when entering Replace mode
• Cursor shapes: 1/2 = block, 3/4 = underline, 5/6 = bar (odd=blink, even=steady)

Example

" Block cursor in Normal mode, bar in Insert, underline in Replace
let &t_SI = "\e[6 q"  " steady bar
let &t_EI = "\e[2 q"  " steady block
let &t_SR = "\e[4 q"  " steady underline

Normal mode: █ (block cursor)
Insert mode: | (thin bar)
Replace mode: _ (underline)

Tips

• For Neovim, use guicursor instead: set guicursor=n:block,i:ver25,r:hor20
• Works in most modern terminals: iTerm2, Alacritty, kitty, Windows Terminal
• Some terminals need tmux passthrough: let &t_SI = "\ePtmux;\e\e[6 q\e\\"
• Reset cursor on exit: autocmd VimLeave * let &t_EI = "\e[6 q"