Be + nominative vs. accusative

Question

I heard that this question causes an eternal conflict between people, and I'd be interested in what you think about it, and whether there is an answer to it or not. (It might have already been asked on the site, in that case, sorry)

So, my question is, which one is correct:

1. It is I.
2. It is me.

More generally: does the verb "to be" require the nominative or the accusative form?

Unfortunately, in English only pronouns (I, you etc.) have an accusative different from their nominative. How does this work in other languages (e.g. German), which have different forms?

To me, "It is I" sounds a bit too formal. "It is me" is much more common, but is it a correct use of the language?

Which one do you use, and which do you think is correct?

Answer 1

As the accepted answer to the question on EL&U that @Lucian Sava linked indicates, both are now correct, because both are widely acceptable to English speakers.

Unlike French which has the Académie française, there is no single authority that determines what is or isn't correct English. Respected dictionaries (such as the OED) are close, but even they rely on what English speakers consider acceptable and correct. For example, in September 2016 the following words were added to the OED:

• bracketology
• clickbait
• moobs
• non-apology
• slacktivism
• YOLO

^{Source: New words list September 2016}

While they're generally not going to be acceptable in formal writing, those words have gained such widespread use and acceptance that the OED saw fit to include them.

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However, just because both are correct doesn't mean you should use both.

It's me.

This is the form you're most likely to hear and should use.

It is I.

In most contexts, this form would sound theatrical or dated, and probably shouldn't be used. It's acceptable in formal contexts, too, but it is (as @BillJ says) very formal.