Vim - Convert text to lowercase or uppercase

To convert all text to lowercase in vim do

ggVGu

or uppercase

ggVGU

look at the command ggVG is used to select all the text if you want you can select the text and use U or u to convert what was selected to uppercase or lowercase.

If you want use this function in search/replace, do this to lowercase (example)

:%s/[A-Z]/\L&/g

or to uppercase (example)

:%s/[A-Z]/\U&/g

Or if you want use this function in character, you can switch case doing this in character

~

Related protips:

Basic Vim commands - For getting started