The one importing pays the tariffs. If that is a person, say buying directly from AliExpress or some other site, then that person pays.
If it's a company, the company pays and might pass it on.
Edit: to be accurate, the importer is legally responsible for the customs declaration and the tariffs, regardless of who does the declaration and who pays. Typically someone else does the declaration on your behalf, and typically they forward any tariffs to you.
