Refers to a test of US personal jurisdiction set forth in a 1997 Western District of Pennsylvania trademark case, Zippo Manufacturing Co. v. Zippo Dot Com, Inc. The Zippo case dealt with a website, Zippo.com which Zippo Manufacturing claimed was infringing its trademark. Zippo, based in Pennsylvania, was the maker of the famous Zippo cigarette lighter – Zippo.com was a website offering news aggregation services based in California.
The Zippo decision did not address the question of whether there was in fact trademark infringement, possibly because the cost of defending the lawsuit was unjustifiable for Zippo.com. Rather the case addressed was whether Zippo.com could be required to defend the case in Pennsylvania. The court in the Zippo decision established a sort of sliding scale for whether an out of state website operator could be held liable to suit in a Federal District, ranging at the low end from websites that are simply readable and read from the jurisdiction for which jurisdiction would be somewhat unreasonable, to the high end where the website operator had deliberately sought out business in the jurisdiction.
Although a number of US circuit courts have adopted the Zippo test, it can be problematic to apply in practice – the easy cases being those at either end of the scale, but those cases in the middle, where a website operator has done some sales, can be difficult to assess.