“I wish I would have known…”
Think about this for a moment, friends. It doesn’t matter what the speaker/writer wishes they’d known, because the beginning of the sentence makes the whole thing nonsense.
I see it frequently online and in manuscripts, though.
Would have and had do not mean the same thing, and almost invariably, what the writer should have said was, “I wish I had known.” (Occasionally, “I wish I could have known” is appropriate.)
So why is I wish I would have known nonsense?
Well, let me tell you…
Would is either the past-tense of will or an indication of intention. (Could, on the other hand, is either the past-tense of can or an indication of possibility.) What “I wish I would have known” actually means is that the speaker wishes they had been willing to know.
If you can’t make yourself willing to know something, no one can. 🙂
If you mean you wish you’d known about something sooner, say, “I wish I had known.” If you wish specifically that it had been possible for you to know about it sooner, say, “I wish I could have known.”