Do you have to pay the tickets online or at the theater?

You can do either.

You can do both

Both work great

both

One can pay either online or at the theater, but there are assigned seats, so buying tickets early can help you get better seats (especially for a newer or more popular movie)

Either.

You can pay online or in person at the theater.

The have both options. You can reserve seats and pay online. Or just pay when you get there and select your seats then.

You can do either... but it's better to reserve your seats a head of time by going online.

You can do either either, but since you're reserving seats it's a good idea too do it online for really popular movies