The franchise tag is a special kind of one-year contract that only exists in the NFL. Once per offseason, a franchise may elect to tag a player, locking them into a non-negotiated salary for the upcoming season.'
Only players who are about to become free agents can be hit with the franchise tag. The franchise tag can't be used to adjust a player's salary in the middle of their contract.
Generally, teams deploy the franchise tag strategically, opting to lock up a key player for a year if long-term negotiations fall apart.
There are two types of franchise tags. The first is the exclusive tag, which prevents a player from negotiating with any other franchise as they would during the free agency period and pays the player a fully guaranteed salary.'