Some cards and effects can only be activated once per turn. There are three distinct ways in which this limitation is commonly applied.
"Once per turn"
"Once per turn" effects can be identified by the text "once per turn" in their activation conditions.
These kinds of effects can only be used once per turn per card, while that card is face-up in its current location. (Even if that effect's activation is negated, it cannot be activated again that turn.) This restriction only applies to that copy of the card; if a player is in possession of multiple cards with the same name that have the same "Once per turn" effect, they can activate each one during that turn. Additionally, if a card that activated its "Once per turn" effect leaves its current location (the entire field is considered the same location) or is flipped face-down, its effect can be activated again during that same turn.
For example, if "activates its effect, it cannot activate its effect again that turn while it remains face-up on the field. However, if after activating its effect it is destroyed and sent to the Graveyard, then Special Summoned from the Graveyard by " ", it can then activate its effect again during that turn. Similarly, if a player controls two copies of "Barrel Dragon", they can activate the effects of both during the same turn."
"Only once per turn"
- Main article: Only once per turn
"Only once per turn" effects can be identified by one of the following conditions: "You can only activate 1 "X" per turn" or "You can only activate/use [reference to effect] of "X" once per turn" (Japanese: このカード名の (Effect #) 効果は１ターン（デュエル）に１度しか使用（発動）できない。). Cards stating "once per Duel" instead of "once per turn" work in the same way, but apply for the entire Duel instead.
The reference to the effect is most often "the effect" or "this effect", but can also be other references such as "1 of these effects", "each of the preceding effects" etc. depending on the structure of the card's text.
If an effect has this condition, each player can only activate that effect of cards with the same name once per turn. This kind of condition is not affected by cards' names being changed; for example, if "" activates its effect, even its name is changed by " " later that turn, it cannot activate its effect again that turn.
If a card states "You can only use this effect of (card name) once per turn", then even if the activation is negated, you cannot activate it once again. On the other hand, if a card states "You can only activate this effect of (card name) once per turn", that effect can be activated again that turn if its activation is negated.
- Example 1 (Add 1 " " card from your Deck to your hand, except " ". You can only activate 1 "Spellbook of Secrets" per turn. ):
If a player activates "Spellbook of Secrets" and its activation is not negated, this means that player cannot activate the card "Spellbook of Secrets" again during that turn.
- Example 2 (Battle Step, while an attack is occurring: You can banish this card from your Graveyard; negate the attack. You can only use the effect of " " once per Duel. ): During either player's
If a player activates the effect "Bacon Saver", this means that player cannot activate the effect of "Bacon Saver" again during that same Duel, even if the activation of the effect was negated.
"You can only gain this effect once per turn"
These effects can be identified by the text "(You can only gain this effect once per turn.)".
Each player can only apply one effect with this text per turn, even if the cards have different names. For example, even if the player controls both "" and " ", the player can only gain the effect of one to perform an extra Normal Summon.
Most effects with this text allow the player to perform an additional Normal Summon/Set that turn without starting a Chain, but only one of these effects can be gained per turn. The only cards with this text that do not have such an effect are " " (which grants an additional Pendulum Summon) and " " (which allows a player to redo a dice roll).