Which film is this a prequel to?

Neither or either, I think. Just a prequel to the story. So... the book? I don't think they've explicitly said it's a prequel to either film.

That said, both the Depp version and this film are Warner Bros, whereas the 1971 film was Paramount, so if it has to be a prequel to either of the films it'd be the 2005 one... I guess.

It's clearly a prequel to Wilder's Wonka. I've seen it.

There were some little references to Gene Wilder's film.

But at the same time, it did feel like it stood alone a bit. I don't see Timothée Chalamet and Gene Wilder's versions being the same person. The characters are very different.

I haven't seen it, but the Depp version has a good amount of "prequel" portion to it. So if any, I would say Wilder.

I would say it's a prequel to Gene Wilder's based on the look of the Oompa Loompas.

If you pay attention to the trailers where we see the Ooompa Loompa, then the 1971 version is an instant pick. However, the movie comes off very fantasy-like to even be a prequel to that movie. In a way, it could have been a prequel to the 2005 version if you were to remove the 1971 references this movie has since the 2005 version has the fantasy style look to it.

Overall, the movie seems to be its own thing just based off the 1971 version. An alternate prequel if you will, which is so dumb to me. Like why even bother? You were best just having this be its own thing without the 1971 version references.

Thankfully it is a prequel to the Gene Wilder version and not the charmless Time Burton version, as there are several references to that film. At one point Wonka says, "Strike that; reverse it." which is directly from the Wilder version. Also,you hear the song "Pure Imagination" in the underscore several times, and then Wonka sings the song at the end. And, on at least two occasions Hugh Grant's Oompa Loompa says, "Good day sir! I SAID GOOD DAY!" which is again, right from the Wilder version. I would say Warner Bros. made the right move and pretended that the Tim Burton/Johnny Depp movie doesn't exist; if only the rest of us could do the same.

There is nothing about this likable young Wonka to hint that he would turn into a depraved Johnny Depp. He is a dark-haired milder Gene Wilder.