I don't know

idiom

1

—used to say that one does not have the information someone is asking for

"What time does the library close?" "I don't know."

2

informal

—used to express disagreement, doubt, or uncertainty

"I don't like that guy." "Oh, I don't know, he's not really so bad."

She thinks we should go now, but I don't know. Maybe we should wait.