til/vim/breaking-the-undo-sequence.md

Breaking The Undo Sequence

Generally, the sequence of undo-able actions is segmented by command. When entering Insert mode, everything typed until exiting Insert mode is part of a single undo-able segment. If you are going to be typing in Insert mode for a while though, you may want to break it up a bit. Without leaving Insert mode, hit ctrl-g u to mark a break in the sequence of undos.

For example, starting in Normal mode and then typing iabc<CTRL-G>udef<CTRL-G>ughi<ESC> will leave the buffer with:

abcdefghi

Hitting u once will leave the buffer with:

abcdef

Hitting u again:

abc

Hitting ctrl-r:

abcdef

See :h i_CTRL-G_u for more details.