How much cards do yu-gi-oh competition allow in a deck?

In Yu-Gi-Oh! competition, a deck must contain exactly 40 cards. This number includes monsters, spells, traps, and any other card types.

There are also limits on the number of certain cards you can have in your deck:

* Main Deck: You can only have 3 copies of any specific card in your main deck, except for basic monsters which have no limit (like "Elemental HERO Shadow Mist").

* Extra Deck: The number of Extra Deck cards you can have varies depending on the format. For example, in the "Master Duel" format, you can have 15 cards in your Extra Deck, while the "TCG" format allows for 15 cards in the Extra Deck.

Remember that you can't have more than one copy of a card in the Extra Deck.