Polite response to an expression of gratitude

without the slightest bit of politeness; blunt or unrestrained, especially regarding criticism

words of politeness or courtesy, sometimes used as a formality and possibly insincere

don't mention it; there is no need for formalities

don't mention it; a polite response when someone thanks you, meaning there is no need to stand on ceremony

Used as a polite response to thanks or during social interactions, meaning "you're welcome" or "please don't stand on ceremony".