3-Card Blind is a casual format played in Internet forums. A tournament organizer is secretly given the decklist by each participant. After the registration deadline expires, the tournament organizer calculates the result from a round robin tournament where each player plays each other player twice with each player starting once.
The organizer can calculate the result because of the rules of the format making every matchup deterministic:
- A deck only consists of three cards
- Each player starts with all three cards in his hand
- Each player plays with his or her hand revealed
- Players draw cards but do not lose the game for being unable to draw a card (this rule makes Anurid Scavenger a viable card)
- Random effects end in the result most beneficial to the opponent of the owner of the card generating the effect (this rule prevents decks such as Black Lotus, Mana Crypt, Sky Swallower)
- For each win a player gets 3 points, for each draw 1 point and for each loss no points.
The complete results of the tournament are posted after the tournament has been calculated so all players are able to verify the results and may question results if they do not understand the result of a specific matchup.
Various variant formats exist with restrictions as to what cards are available (e.g. only commons are allowed) or specific effects are additionally present (e.g. every player starts every turn with one mana of any color in his mana pool, the mana doesn't burn until end of turn and doesn't cause loss of life as a result of burn).
In general, this format rewards creativity in limited space and metagaming skills.
- Timmy: Black Lotus, Black Lotus, Visara the Dreadful
- Johnny: Black Lotus, Treasure Hunter, Aura of Silence
- Spike: Golgari Rot Farm, Treetop Village, Putrefy
- Timmy vs. Johnny: If Timmy begins he can play Visara first turn and win the race against Johnny's Treasure Hunter or just destroy the Treasure Hunter. If Johnny begins, he can play Lotus, Hunter, Lotus and Aura and Timmy can not play his Lotuses and Johnny just beats him with the Hunter. The Matchup is 3-3.
- Timmy vs. Spike: In either scenario, Timmy can not deal lethal damage before Spike has enough mana to cast Putrefy and destroy Visara. Spike will beat down Timmy with the Village. The Matchup is 6-0 for Spike.
- Johnny vs. Spike: Aura of Silence does not affect Spike at all. As such, Spike can just destroy the Hunter with Putrefy and win with Treetop Village. Spike wins this Matchup 6-0.
 Banned cards and decks
Due to the limitations of the format, certain cards and decks have been made illegal to keep the format interesting:
- Decks that can win first turn
- Decks that let the opponent discard more than one card per turn
- Parody cards from Unglued and Unhinged
- Non-mass produced cards e.g. 1996 World Champion
Further Organizers may have their own specific list of cards banned from use. Even though they depend on the organizers, usually those lists feature the following cards:
- Abandon Hope
- Barren Glory
- Cabal Therapy
- Form of the Dragon
- Ghost Quarter
- Glacial Chasm
- Leonin Squire
- Meddling Mage
- Mesmeric Fiend
- Nezumi Shortfang
- Pulse of the Dross
- Restore Balance
- Show and Tell
- Strip Mine
- The Rack