Which format is most likely to require Swiss pairing?

Swiss pairing is primarily used in tournament formats where players compete in a set number of rounds, and the results of each round are used to match players against others of similar records in subsequent rounds. This format facilitates a more balanced competition, allowing players to face opponents that have had similar success in the event.

Constructed events, specifically those that operate in Swiss format, often feature multiple rounds of play where players build their decks ahead of time using their card pool. The Swiss pairing system is particularly suitable here because it allows players to continue competing even after losing a match, ensuring that they can play several rounds against various opponents before a final outcome is determined.

In contrast, other formats such as Single Elimination only pair players for one match or a series leading to a knockout situation. Booster Draft events might also use Swiss pairing, but they are typically structured differently, and Two-Headed Giant involves teams rather than individual competitors facing off against one another. Therefore, among the options provided, constructed events are the most common setting to utilize Swiss pairing effectively, as they embody the principles of continuous play based on performance.