You lose game one badly. Your opponent's deck did something your list simply cannot handle. Then you remember the small stack of extra cards sitting next to your deck, and you have a few minutes to decide what to do with them.
That stack is your sideboard, and using it well is one of the biggest skill gaps between casual and competitive players. Best-of-three matches reward the player who adapts between games, not just the one with the stronger list. Here is how to sideboard with a plan instead of a panic.
🗃️ What is a sideboard and how does it work?
A sideboard is a small set of extra cards you can swap into your main deck between games of a match. In most formats you play game one with your main deck as built, then you may exchange cards before games two and three.
Rules vary by game and format, so always check the official rules for what you play. In Magic: The Gathering constructed play, for example, a sideboard may contain no more than 15 cards, and the four-copy limit counts your main deck and sideboard together (Comprehensive Rules, as of November 2026). Digital clients that support best-of-three usually include a sideboard section in the deck editor.
The usual swap is one-for-one: one card comes in, one card goes out, so your deck stays at the same size. That keeps your curve and resource ratio stable, which matters more than many players think. It also makes it easy to double-check your deck count before the next game starts.
🎯 What should go into a sideboard?
A good sideboard card solves a specific problem your main deck struggles with. It is usually too narrow for the main deck but very strong in the right matchup.
Common categories:
- Hate cards: Cards that punish a specific strategy, such as graveyard removal against decks that reuse cards from the discard pile.
- Extra removal: More answers for threat-heavy matchups, often of a type your main deck runs only lightly.
- Early defense: Cheap blockers or sweepers against aggressive decks.
- Late-game power: Extra card advantage or threats for long, grindy matchups.
- Flexible swaps: Cards that change your deck's role, like more aggressive threats against slow control decks.
Be careful with cards that only answer one deck you rarely see. A slot spent on a card for a matchup that comes up once per event is a slot that could have helped against the deck you face every other round. The best sideboards lean on cards that cover two or three problems at once, like a cheap removal spell that is good against both aggro creatures and certain engine pieces.
Start by listing the three to five decks you expect to face most. For each, write the problem it creates for you. Your sideboard should answer as many of those problems as possible, ideally with cards that help in more than one matchup.
✂️ What should come out of your main deck?
This half gets less attention, but it matters just as much. Taking out the wrong cards is how a good sideboard plan turns into a weak deck.
Look for cards that are bad in this specific matchup:
- Removal that has no good targets against the opponent's deck.
- Slow, expensive cards against a fast aggro opponent.
- Small, fragile creatures against a deck full of cheap sweepers.
- Combo pieces that the opponent can easily disrupt.
A useful question: "If I drew this card on turn three in this matchup, would I be happy?" If the honest answer is no, it is a candidate to come out.
Keep an eye on your resource count while you swap. If you bring in three cheap cards and take out three expensive ones, your deck gets lower to the ground, and in games with resource cards you might be able to trim one of those too. The opposite also holds: bringing in heavier cards may mean you want to keep every resource card you have. Small curve shifts like this are part of sideboarding, even though they rarely get discussed.
Also think about synergy before cutting. Some cards look weak alone but power up others. Removing one piece of a synergy package can quietly weaken several remaining cards, so treat linked cards as a group when you decide what leaves.
Tip: Write your sideboard plan before the event, in a note on your phone or on paper, with "in" and "out" lists for each common matchup. Between games you will be tired and rushed, and a plan you made calmly is better than one made under pressure.
🔁 How does being on the play or the draw change things?
In most card games, going first gives a tempo advantage, while going second gives you an extra card or a small resource boost. That difference can shift what you want in your deck.
| Situation | What often changes | Example adjustment |
|---|---|---|
| On the play vs. control | You want to apply pressure early | Bring in extra cheap threats, cut slow answers |
| On the draw vs. control | You have more cards for a long game | Keep card advantage pieces in |
| On the play vs. aggro | You can develop first and block | Fewer cheap blockers may be needed |
| On the draw vs. aggro | Opponent is ahead on tempo | Bring in more cheap removal and early defense |
You do not need a separate plan for every case, but noticing the difference can turn close matchups. In many events, the loser of the previous game chooses who starts next, so you can often predict the situation before you even begin swapping cards. Experienced players sometimes swap one or two extra cards depending on who starts.
⚠️ What is overboarding and how do you avoid it?
Overboarding means bringing in so many sideboard cards that your deck loses its identity. It is one of the most common mistakes in best-of-three play.
Signs you have overboarded:
- Your deck no longer has enough threats to actually win the game.
- Your curve went from smooth to lumpy because you swapped cheap cards for expensive ones.
- You removed key synergy pieces, so your remaining cards are weaker.
A rough rule of thumb many players use: if you are swapping more than a third of your deck, double-check that the plan still works. Sometimes a big swap is correct, for example when changing roles against a specific deck. Often it is a sign of panic, usually after one painful loss where a single card or a lucky draw made the matchup look worse than it really is.
The fix is simple: for every card you bring in, ask whether it is clearly better than the card it replaces in this matchup. "Slightly better" is often not worth disrupting the deck's flow.
🕵️ How do you think about your opponent's sideboard?
Sideboarding is a two-player game. While you adjust, your opponent does too, and good players anticipate that.
Questions to ask before game two:
- What did they struggle with in game one? They will likely bring in answers to that.
- What cards might they add against my deck? If your deck is weak to a certain type of hate card, consider keeping a way to handle it.
- Will they change roles? A control deck might bring in more threats and act faster after sideboarding.
Pay attention to what you see in games two and three. If a surprise card shows up, remember it for the next time you face that deck or that player.
Game three adds one more layer. You have now seen part of their sideboard plan, and they have seen part of yours. Some players change a card or two again based on what showed up, for example cutting a creature that died to a specific answer and bringing in one that dodges it. Small reactive tweaks like that can matter in a deciding game, as long as they do not snowball into a full rebuild.
🧾 A simple between-games routine
Matches often give you only a few minutes between games. A routine keeps you calm and fast.
- Note what lost or won game one in one sentence
- Check your written plan for this matchup
- Swap cards one-for-one and count your deck afterward
- Shuffle thoroughly and present your deck on time
- After the match, return every card to its original place
That last step is easy to forget. Starting the next match with a sideboarded deck by accident has cost many players a game one.
🏁 Sideboarding with purpose
A sideboard is a set of precise answers for the matchups you expect. Use it to fix specific problems, take out cards that are weak in the matchup, and keep your deck's identity intact.
If you are new to best-of-three, start small. Pick the two decks you face most, build a simple in-and-out plan for each with three or four swaps, and stick to it for a few events. Once those plans feel natural, expand to more matchups and finer adjustments like play-or-draw changes. Trying to master everything at once is how players end up making rushed swaps they regret.
Plan ahead, write it down, and think about what your opponent will do too. Over a whole event, those small adjustments add up to a lot of extra wins.
❓ Frequently Asked Questions
Do I have to use my sideboard every match?
No. If your main deck is already well positioned against your opponent, you can keep it as is. Sideboarding is a tool, not a requirement.
Can I sideboard before game one?
In most formats, no. Game one is played with the main deck as registered, and swaps happen only between games. Check the rules of your specific event to be sure.
How many copies of a sideboard card should I include?
It depends on how important the card is in the matchup. Two or three copies of a strong answer to a popular deck is common, while one copy works for niche situations.
What if I face a deck I did not prepare for?
Think about its plan and which of your sideboard cards answer that plan in general terms. Cheap removal, early defense and card advantage are flexible enough to help against many unexpected decks.