| Main Deck
When constructing a Deck, Monster, Spell and Trap Cards are placed in the Main Deck. (Fusion, Synchro and Xyz Monsters are placed in the Extra Deck. If a player uses official Token Monster cards, these are to be stored in a separate location as well.)
When a Duel begins, the Main Deck is placed face-down in the Deck Zone of the Field. All cards in the Main Deck must remain face-down during the Duel (unless a card effect like "Convulsion of Nature" says otherwise). During a Duel, neither player may view the contents of either player's Deck unless a card effect allows them to, after which the Deck must be shuffled. Even if a card in the Deck is face-up, it cannot be looked at by either player unless it is on top of the Deck, in which case it is public knowledge.
Main Deck construction restrictions
Constructed Deck format
- The Main Deck must contain only Legal cards.
- The Main Deck can have a minimum of 40 cards and a maximum of 60 cards. (Only the cards in the Main Deck, not cards in the Extra Deck, count toward this total.)
- A Duelist may not have more than three copies of any Unlimited card included in their Main Deck, Side Deck, and Extra Deck combined.
- If a Forbidden, Limited, or Semi-Limited List is used, the number of copies must not exceed those requirements.
- Cards which have their name permanently treated as that of another card are considered to be the same as that card for deck construction.
Sealed Deck format
- The Main Deck must be constructed using only card product provided at the event.
- The Main Deck can have a minimum of 20 cards. There is no maximum size.
- A Duelist may include as many copies of any card he or she likes, even more than three.