First to file (FTF) and first to invent (FTI) are legal concepts that define who has the right to the grant of a patent for an invention. The first-to-file system is used in all countries. There is an important difference between the strict nature of the FTF under the European Patent Office (EPO) and the FITF (First inventor to file) system of the United States Patent and Trademark Office (USPTO). The USPTO FITF system affords early disclosers some "grace" time before they need to file a patent, whereas the EPO does not recognise any grace period, so early disclosure under the FITF provisions is an absolute bar to later EPO patent.