The IDK full form is I Don’t Know. His phrase is commonly used in a variety of contexts, such as mobile text messaging, Internet chatting, and so on. There are no specific standards for this statement, and it denotes someone’s ignorance about something.

I = I

D = Don’t

K = Know

Example:

Amit: Do you know a Chinese restaurant?

Anu: IDK, I am not sure.

• “I Don’t Know” is a song by Paul McCartney, released as a double A-side single opposite “Come On to Me” by Capitol Records ahead of McCartney’s 17th studio album, Egypt Station.
• “I Don’t Know” is characterized on McCartney’s website as a “plaintive, soul-soothing ballad as only Paul can provide.”
• McCartney stated in his ‘Casual Conversation with Jarvis Cocker at LIPA’ (25 July 2018) that he believes John Lennon would enjoy this song.