??? but i would snip off those leaves and toss them in the trash in case it's infectious.

Hi, did you ever figure this out? I have the exact same spots on my basil leaves, and I can't find any answers online.

Black spotting on basil leaves is usually an early indication of downy mildew.

Thanks! I've read that spotting on the under side of leaves is typical with downy mildew. You think these spots on the topsides is also downy mildew?

What's your soil pH like? The leaves look pretty yellow. Have you fertilized?

Do you by any chance mist or spray the leaves?

It looks cultural to me, like cold damage from fog or mist.

I do grow basil and I have often seen this thing often. It is not a serious problem but just cold damage or fertilizer problem. I would suggest you change the fertilizer you are using.