Recently, the rules for the Yu-Gi-Oh! TCG have changed slightly. The change affects how duelists can make use of their Side Deck.
Under the previous version of the rules, players could modify their Main Decks during a Match by swapping cards between Main Deck and Side Deck after each Duel. Now, players are also allowed to modify their Extra Deck the same way, by swapping cards between Extra Deck and Side Deck. However, only Synchro or Fusion Monsters can be added to the Extra Deck this way.
The new wording of the Side Deck rules is:
“Side Deck (0 to 15 cards)
This is a separate Deck of cards you can use to change your Deck during a Match. After each Duel in a Match, you can swap any card from your Side Deck with a card from your Deck and/or Extra Deck to customize your strategy against your opponent. The number of cards in your Side Decks must not exceed 15. The number of cards in your Side Deck before and after you swap any cards must be exactly the same.”
The new rules are documented on page 2 of the current rulebook, which can be found in the “rulebook” section of our webpage, http://www.yugioh-card.com.
The change is effective immediately and will be used for all official Konami tournaments.