IDP leagues are a type of fantasy football that uses individual defensive players rather than full defensive units. They are not as popular as standard leagues but have existed for just as long, since defensive players were part of the first ever fantasy rosters in 1962. IDP leagues require a lot more work of the team owners than typical leagues due to the enlarged rosters.
IDP leagues will usually feature only a few roster spots for each defensive position group, which not only means that there is a lesser demand to get them high in the draft but that there are plenty of solid players on the waiver wire and in free agency each week. This allows for owners to be more cognizant of matchups and be fluid with their defensive units. A common breakdown for a roster includes three members of the secondary, three linebackers, and two linemen.
Scoring systems are not standard by league, but the general values are around one point per pass defended, 1.5 points per tackle, 0.5 points for an assist, two points for a fumble recovery or forced fumble, four points for a sack or interception, and six points for a defensive touchdown. Advanced leagues will assign different points for each accomplishment depending on the position of the player who did it.
One main distinction is that team defenses in standard leagues also are awarded points for the heroics of special teams, usually just return touchdowns, but in some cases yards. This aspect is nonexistent when using individual players.
IDP leagues require a larger knowledge base of the NFL than their standard counterpart since the offense is no longer the only facet of the game.