Wrap Existing Text at 80 Characters with Vim

You have an existing block of text or code in Vim. You want to re-format it to wrap to 80 characters.

:set textwidth=80

Select the lines of text you want to re-format:

v

Reformat it:

gq

Learn more:

:h gq

If want the 80 character setting to apply automatically for file types like Markdown, add this to your vimrc:

au BufRead,BufNewFile *.md setlocal textwidth=80