An inventor has to be very careful about disclosing their invention to others before filing a patent application. For example, if an inventor uses an invention in public or offers the invention for sale more than one year before filing a patent application, that public use or offer for sale may interfere with the inventor’s ability to obtain a patent in the U.S. Many foreign patent offices are even stricter. These foreign offices do not provide the inventor the one year grace period offered by the US. Instead, any public disclosure before filing the patent application will eliminate the possibility of getting a patent.
So, if an inventor were to give a public demonstration of their invention or describe their invention on a public website, that inventor would have exactly one year to file a patent application in the U.S. or potentially forfeit their patent rights. That same inventor would also be barred from obtaining a patent in Europe even if the inventor filed the patent application a day after the public demonstration or the date the website became public.
Not surprisingly, many inventors are not aware of these strict rules and make the mistake of showing their invention publicly too early. When there is a choice, it is always best to file a patent application before showing your invention to the public or offering it for sale. Once a quality patent application is filed, the situation changes and it is much safer to show your invention to the rest of the world.