How do you insert a newline after every 80 characters in vim?

:%s/.\{80}/&\r/g

• %: process the entire file
• s: substitute
• .: matches any character
• {80}: matches every 80 occurrences of previous character (in this case, any character)
• &: the match result
• \r: newline character
• g: perform the replacement globally

You can also modify this approved answer to only insert the newline at the first space occurring after the 80th character:

%s/\(.\{80\}.\{-}\s\)/\1\r/g

Using regular expression:

:%s/\(.\{80\}\)/\1\r/g

Using recursive Vim macro:

qqqqq79la<Enter><esc>@qq@q


qqq  Clear contents in register q.
qq   start marco in register q
79la<Enter> Carriage return after 80 characters.
<esc> go back to normal mode
 @q   run macro q which we are about to create now.
 q   complete recording macro
 @q run macro