I have a really good idea for the optional essay–super unique, representative of me and the way that I think, and also emphasizing what I want to do at Harvard and beyond. It’ll incorporate another essay that I’ve written for class which was 3 pages long, so I’m expecting my Harvard essay to be of similar length. Is this okay?
I know someone who wrote an optional essay that was one paragraph. I am sure there is a lot of variation but three pages sounds too long. This is really to cover anything the rest of the application doesn’t cover, such as an interest or a challenge that isn’t described elsewhere.
Be careful about trying to be “unique.” You may very well succeed but in my tutoring experience with essays, attempts to be unique often do not produce good essays.
Think about what Harvard doesn’t know about you, in fairly specific terms, after the rest of the application is done, and focus on that.