Shuffle

Shuffle is a keyword action that was introduced in Alpha. A shuffled deck must be completely randomized. Libraries can only be shuffled when a player is directed to do so by the rules. Players shuffle in many different ways. The most common is a combination of 'riffle' shuffles and 'pile' shuffles.

Description
Before each game, each player must shuffle their deck. While the Comprehensive Rules state only that libraries must be in a state such that no player knows their order, the Tournament Rules go into substantially more detail. Notably, the Tournament Rules state that pile shuffling alone is not adequate. Additionally, players must have the option of performing a final shuffle of their opponent's deck. At the Competitive and Professional Rules Enforcement Levels, players must shuffle their opponents decks.

During the game, various effects may require a player to shuffle their library again. This usually follows a player searching that library, and is necessary to avoid that player accurately predicting every draw from that library. Outside of search effects, several cards direct that some set of cards be shuffled into the library from other zones.

R&D tries to minimize the frequency of shuffle effects by avoiding printing them at lower rarities, because they slow down the pace of play, and because many new players are uncomfortable with shuffling.