A club's active roster is comprised of up to 30 players. All 30 players are eligible for selection to each 18-player game-day squad during the 2018 MLS regular season and playoffs.
SENIOR: (ON-BUDGET) Up to 20 players, occupying roster spots 1-20, count against the club's 2018 Salary Budget of $4,035,000 (USD), and are referred to collectively as the club's Senior Roster.
SUPPLEMENTAL & RESERVE: (OFF-BUDGET) The salaries of players on the Supplemental Roster (spots 21-24) and Reserve Roster (spots 25-30) do not count toward a club's Salary Budget.
INTL: In 2018, a total of 184 international roster spots are divided among the 23 clubs. These spots are tradable, in full season increments, so some clubs may have more than eight and some clubs may have fewer than eight.
DP & Young DP: The Designated Player Rule allows clubs to acquire up to three players whose total compensation and acquisition costs exceed the Maximum Salary Budget Charge, with the club bearing financial responsibility for the amount of compensation above each player's Salary Budget Charge. A Designated Player 23 years old (or younger than the age of 23) during the League Year is a Young Designated Player Budget Charge. Designated Player spots are not tradable.
HG: A club may sign a player to a contract without subjecting him to the MLS SuperDraft if the player has been a member of a club's youth academy for at least one year and has met the necessary training and retention requirements. Players joining MLS through this mechanism are known as Homegrown Players.
GA & GA-C:Generation adidas (GA) and Generation adidas Canada (GA-C) are joint programs between MLS and adidas that are dedicated to developing exceptional domestic talent in a professional environment. Until a player graduates from the program, Generation adidas players are on a club's Supplemental Roster and are not charged against the team's salary budget.