sideboarding

Sideboarding is the practice of using a separate set of cards, the sideboard, to modify a player’s main deck between games in a match. The aim is to tailor the deck to counter an opponent’s strategy, address specific threats, or improve a matchup that is unfavorable in the first game. Sideboarding allows players to keep the core plan of their deck while adding or removing tools as needed.

In Magic: The Gathering, the standard format for constructed play uses a maindeck of 60 cards and a sideboard of up to 15 cards. A match in a best-of-three format typically allows players to swap cards between the maindeck and the sideboard after the first game and again after the second, so long as the maindeck ends up with 60 cards and the sideboard remains within its limit. Sideboard changes are made between games and the sideboard cards are not drawn during games; only cards from the maindeck are drawn.

Typical sideboard content includes answers aimed at common threats, such as removal or counterspells for aggro or control decks, graveyard hate for graveyard-based strategies, artifact and enchantment destruction, or mana-base tweaks to fix color issues. The exact choice of sideboard cards depends on the metagame and the expected opponents.

Practically, players prepare their sideboard strategy in advance and execute changes with careful attention to rules and deck size limits. While sideboarding is most associated with Magic: The Gathering, similar concepts exist in other tournament formats that use best-of-three matches and separate sideboard libraries to adapt to opponents.