Reference

How Two-Headed Giant works

Two teams of two. Each team shares one life total and takes one turn together. That's the whole format — and it's enough to change what half the cards in Magic are worth.

The core rules are the same in every variant. The numbers aren't: a team starts at 30 life in Sealed and Draft and at 60 in 2HG Commander. Pick your format below for the rules specific to it.

Three ways to play, one set of core rules

The rules every variant shares

One life totalCR 810.9, 810.8c: Teammates share a single life total. Damage, life loss and lifegain happen to each player and land on the team's total, and the team loses when it hits 0.
One turnCR 805.4, 805.5: The team takes its turn together. Each player draws in the team's draw step and may play a land, and either teammate can act whenever the team has priority.
The starting team doesn't drawCR 810.6: The team that goes first skips the draw step of its first turn — both players skip it, not just one.
Two opponents, one totalCR 810.9, 102.3: 'Each opponent' resolves against both players on the other team, and both results come off one shared life total. A drain of two takes four.
Attacks pick a playerCR 805.10: Each attacking creature attacks one specific opponent, planeswalker or battle. The defending team blocks as one, with creatures from either player.
One player loses, the team losesCR 810.8a, 810.8b: If either player loses — drawing from an empty library, say — the whole team loses. A concession takes the team out too.
Your teammate is a legal targetCR 810.5: Spells and abilities can target your teammate and their permanents. Hands can be shown and plans discussed at any time, but you can't handle each other's cards.
Poison is 15CR 810.10, 810.8d: Poison counters are shared by the team, and a team loses at 15 rather than the usual 10, so infect and toxic clocks are slower than their raw numbers suggest.

Where the formats differ

Rule	2HG Commander	2HG Sealed	2HG Draft
Shared starting life	60	30	30
Each deck	100 cards, singleton	40+ from one pool	40+ from the drafted pool
Built	At home	At the event	At the event
Same card in both decks	Allowed	One copy, one deck	One copy, one deck
Commander damage	21 from one commander	—	—
Poison to lose	15	15	15
Where it's played	Monthly Commander Night	Prereleases	Store drafts

The one rule people get wrong

2HG Commander has no unified deck rule. Wizards' event rules say you may bring any legal Commander deck, so you and your teammate can both run Sol Ring — the singleton rule applies to each deck, not to the team. The cross-deck rule people remember belongs to 2HG Constructed, a different format entirely, and doesn't apply to anything you'll play at a Commander Night.

Common questions

What is Two-Headed Giant in Magic: The Gathering?

Two-Headed Giant is a team format for four players: two teams of two. Each team shares one life total, takes its turns together and attacks together. It is played as Sealed at prereleases, as Booster Draft, and as 2HG Commander at monthly WPN events.

How much life does a team start with in Two-Headed Giant?

30 in standard Two-Headed Giant, which covers Sealed and Draft. 2HG Commander uses 60, per Wizards' format page. In both cases the total is shared, so damage to either teammate comes off the same pool.

Do both players draw a card in Two-Headed Giant?

Yes. Each player draws one card in the team's draw step and may play a land each turn. The exception is the team that goes first: both of its players skip the draw on that team's first turn.

How do “each opponent” effects work in 2HG?

They affect both players on the other team, one at a time, and both results come off the opposing team's shared life total. A card that makes each opponent lose 2 life takes 4 from that team.

Can you choose which player to attack in Two-Headed Giant?

Yes. Each attacking creature attacks one specific opponent, planeswalker or battle, chosen as attackers are declared. The defending team blocks together, using creatures from either player, and combat damage reduces the shared life total.

If one player decks out in 2HG, does the whole team lose?

Yes. Teams win and lose together. If either player loses the game, for example by drawing from an empty library, the whole team loses. If either player concedes, the team leaves the game.

Do teammates share mana or cards in Two-Headed Giant?

No. Only the life total and poison counters are shared. Each player keeps their own hand, mana and permanents. Teammates may look at each other's hands and talk strategy at any time, but can't handle each other's cards.

Is the first mulligan free in Two-Headed Giant?

Yes. Two-Headed Giant is a multiplayer game, and in multiplayer games each player's first mulligan is free. Each player decides separately, and teammates may consult before deciding.

Sources

Rules summarised from Wizards of the Coast's Comprehensive Rules, Magic Tournament Rules and format pages. Where a store runs house rules, theirs win.