Tom Clancy's Rainbow Six Siege is a first-person shooter game, in which players control an operator from the Rainbow team. Different operators have different nationalities, weapons, and gadgets. The game features an asymmetrical structure whereby the teams are not always balanced in their ability choices. The Counter Terrorism Units (CTUs) available for play include the FBI Hostage Rescue Team, the British SAS, German GSG-9, Russian Spetsnaz and French GIGN, each of which has four operators per unit (other units were later added through downloadable content, see below). Players also have access to a "Recruit" operator who can choose from a more flexible assortment of equipment at the expense of having no unique gadget. Players pick an operator from any unit before a round starts, and are not allowed to change operators during a round. An in-game shop allows players to purchase operators using the in-game currency, "Renown", which is earned at the end of matches from actions performed in-game. The different gameplay modes award renown at different rates, with ranked matches offering the largest renown multiplier potential per match. Renown can also be affected with the addition of "boosters" which give the player a 100% increase in all renown earned for 24 hours (real time not play time). . Renown can be used to purchase weapon customization options, which allow players to put attachments such as silencers and scopes on their weapons. A premium credit, known as "R6 credits" can also be purchased using real world currency to get operators quicker in-game, or other cosmetic.
In ranked play, when a round begins, the attackers choose one of several spawn points from which to launch their attack. The attackers are then given control over wheeled drones to scout the map in search of enemy operators and targets, while the defenders can use security cameras to spot the attackers. Maps in the game are designed to encourage close quarters combat, and players cannot respawn until the end of a round. Defenders can also put up destructible barricades and reinforce walls to make them indestructible unless you have an appropriate operator. Players who were killed by opponents can enter "Support Mode", which allows them to gain access to drone's cameras and security cameras so that they can continue to contribute to their team by informing them of opponent locations and activities. Matches generally last only a few minutes. Teamwork and cooperation is encouraged in Siege, and players need to take advantage of their different abilities in order to complete the objective and defeat the enemy team. Communication between players is also encouraged. The game also has a spectator mode, which allows players to observe a match from different angles.