case sensitive (also written as case-sensitive)
noun phrase

- if a computer program is case sensitive, it can recognize if a letter is a capital or a small letter

(Cambridge Dictionaries)

---
Case sensitive refers to text or input text that is capitalization sensitive. In other words, "Paul" and "paul" are two different words because the "P" is in uppercase and lowercase. A password and username is often case-sensitive. This means your username or password must have the proper case or you will be unable to login. If you're unable to log into a computer or service make sure your caps lock key is not on and that you're using the correct case.

Anything that is not case sensitive means that any uppercase or lowercase character can be entered. For example, the Windows command line or MS-DOS is not case-sensitive. However, the Linux command line is case sensitive. You could type "cd", "CD", "Cd", or "cD" for the cd command in the Windows command line without error, but only "ls" will work for the ls command in Linux, typing in "LS" would generate an error.

www.computerhope.com

---
SMUGGLE OWAD into today's conversation

"The login is case sensitive, so make sure you pay attention to capitalization when logging into your account."

---
Thanks to Volker for suggesting today's word!