The maximum number of players a team can dress for an NHL game is 20.
That total normally consists of 18 skaters and two goaltenders. The skaters are forwards and defensemen, while the two goaltenders provide the starter and backup positions. Teams submit their eligible players before the game, and only those listed players can normally take part.
The 20-player game lineup is different from an NHL club's active roster. During much of the regular season, a team may carry up to 23 players on its roster, but only 20 can be dressed for a particular game. The three players left off the lineup are commonly called healthy scratches, unless they are unavailable because of injury, suspension, or another roster designation.
The limit also explains a familiar late-game tactic. When a team pulls its goaltender, it can place a sixth skater on the ice, but that does not increase the number of players dressed. The team is temporarily using one of its two goaltenders as an extra attacker. Under unusual emergency circumstances, league rules contain special provisions for goaltender substitutions, but the normal maximum remains 20 players.