I have some questions about Sideboarding, especially in Limited sideboarding, that I would like to know the answers to. The speed at which players sideboard, and how much time is spent adding and removing cards to the deck can reveal a rough indication of how many cards are sideboarded. In constructed, typically this gives little information; it's easy even to misdirect someone who attempts to gain information this way (just spend as much time as it would take to sideboard say 12 cards when you're only switching 2). It's hard not to notice boarding is happening or when it is done, and one player inevitably is faster than the other.

The interesting question is what happens with Limited, and fringe or linear strategies. Two examples are Lost in the Woods (Innistrad dark ascension) and Mill. Say one player is playing heavy into mill. They're mulling over what to sideboard and notice the opponent having shuffled their deck and putting down a very thick stack of cards. Their opponent turned their 40-card draft deck into a 65-card one. Is it wrong to act upon this information? How would you even prove someone did, as it's not that weird to sideboard out a mill strategy when hate against it is universal due to the rules for Limited. Or, if you're the player playing mill, and the information is supposed to be hidden, whether you intended to cheat or not gets muddy when the decision to continue with mill or switch up the deck is strategically contentious.

Another example, which I don't know if it ever came up, is two copies of Lost in the Woods in the same draft facing each other, with either player not having any enchantment removal. If both players decide to stick with it or return to it in game #3, #4 or #7, whoever has the biggest library wins. And since you can add any number of forests, and see 49 cards using mulligans, and both players attempt to do this, thus the sideboarding never ends, or I guess whoever has the biggest hands (as in, physically) wins, which is just weird.

  • 1
    Why do you say "Into the Woods" when the card you linked to is "Lost in the Woods"? And what does that card have to do with mill or having a larger deck? It doesn't change the number of cards in your deck. Jul 27, 2022 at 13:29
  • @ArcanistLupus Lost in the Woods makes it so that you can't lose to combat damage, so if both players have one out (and they aren't playing direct damage) then whoever has the larger deck will win.
    – GendoIkari
    Jul 27, 2022 at 13:45
  • @Arcanist Lupus It's because of an earworm from a certain movie that came out a couple years after Innistrad that I conflate that card's name all the time. Doesn't help that half of the movie is spent singing it.
    – aphid
    Jul 27, 2022 at 17:55

2 Answers 2


You are allowed to use information revealed by your opponent, but you may not acquire such information actively. You may not delay sideboarding indefinitely.

As per the Magic Tournament Rules, sideboarding is part of the pregame procedures.

2.3 Pregame Procedures

The following steps must be performed in a timely manner before each game

  1. If sideboarding is allowed, players may remove cards from their sideboards.

  2. Players shuffle their decks. Steps 1 and 2 may be repeated.

  3. [..]

You are allowed to use any information revealed by your opponent, whether the reveal was intentional or not. You may not attempt to find out such information actively.

3.13 Hidden Information

Hidden information refers to the faces of cards and other objects at which the rules of the game and format do not allow you to look. Throughout the match, a draft, and pregame procedures, players are responsible for keeping their cards above the level of the playing surface and for making reasonable efforts to prevent hidden information from being revealed. However, players may choose to reveal their hands or any other hidden information available to them, unless specifically prohibited by the rules. Players must not actively attempt to gain information hidden from them but are not required to inform opponents who are accidentally revealing hidden information.

As already quoted in rule 2.3, the pregame procedures including sideboarding must be completed in a timely manner. They are subject to the time limit of each round of matches. A judge can give out warnings for slow play for either player if either or both of you go back and forth about sideboarding without completing it.


Is it wrong to act upon this information?

No, you're free to use the information. It's why it's advisable to conceal how you are sideboarding, and why some players will just swap some basic lands to hide the fact that they're not sideboarding.

If it comes to it you can both sideboard with your backs turned, and once both players are done sideboarding no more changes can be made (even if opponent clearly has a 200-card deck).

You must log in to answer this question.

Not the answer you're looking for? Browse other questions tagged .