Is it “than I” or “than me”?

Short answer: It’s both!

“Than” in these constructions can function as a conjunction or a preposition, which just means you can end a sentence like:

“This person is better at spelling than I am.”

OR

“This person is better at spelling than me.”

And be right either way. All you have to do is decide if you want to sound more formal (I) or casual (me).

For more information, as usual, just ask Merriam Webster!