The caps lock key is a key on a computer keyboard used to toggle capitalization of letters while typing. It has several synonyms, including the all-caps key, uppercase key, and shift lock key. The acronym CL is a shorthand for the caps lock key, and some may also refer to it as the caps key. The caps lock key is often used in combination with the shift key to type entire words or phrases in capital letters. However, its constant use can make writing seem like shouting. Nowadays, some keyboards don't feature a caps lock key, replacing it with a search key or other functions.