How do I toggle the case of an entire word in Vim?

Explanation

The g~iw command toggles the case of every character in the word under the cursor — uppercase letters become lowercase and vice versa. This is faster than visually selecting the word and pressing ~ on each character.

How it works

• g~ is the toggle-case operator
• iw is the "inner word" text object, selecting the word under the cursor
• Together they flip the case of every character in the word

Example

Given the text with the cursor on Hello:

Hello World

Pressing g~iw produces:

hELLO World

Pressing g~iw again on the same word restores the original:

Hello World

Tips

• Use g~$ to toggle case from the cursor to the end of the line
• Use g~~ to toggle case of the entire current line
• gUiw forces the word to UPPERCASE, guiw forces it to lowercase
• gU and gu accept any motion: gUap uppercases a paragraph, gu$ lowercases to end of line
• The ~ key by itself toggles the case of the single character under the cursor and moves right
• Pair with . to repeat on the next word: g~iw then w.w. to toggle successive words