What does 'How didn't I know this song before' means?

Question

So...here I watched a song on YouTube and that song was released a year ago and that song was lit! So what should I say there ? 'How didn't I know this song before/till now?" Or "how couldn't I know this song before/till now?" Which one is correct to say? (I want to express my surprise that I didn't know that song till today and how it happened? Because I'm a fan of that singer and I should have known that song) or anything that is correct. Please answer.

Btw, if you're wondering which song I watched today? Then the answer is, Dip by Meng Jia. You can go and listen to it.

And well do me an another favour, please tell me which one is correct! Listen song on YouTube or watch song on YouTube? I'm always confused about this. Because you both listen and watch on YouTube so... Lol answer me asap please.

Answer 1

you couldve said " i souldve known this song by now"

you listen to songs on youtube but you can watch the music video

Answer 2

Either is grammatically correct but it will sound more natural if you move "not".



How did I not know this song already!?

How could I have not known about .....

Answer 3

how did i not know this song till now :)