Magic's Comprehensive Rules document defines a mulligan, and details the circumstances and process for taking a mulligan.

According to the glossary: "To take a mulligan is to reject a prospective opening hand in favor of a new one. See rule 103.5"

The full text of rule 103.5 is a substantial wall of text. Let's start with a short summary:

At the start of a game, players draw a hand of cards. Then, in turn order, they declare whether they are taking a mulligan. Players take mulligans by shuffling their unwanted hands back into their libraries. For every mulligan a player takes, that player must put one card from their starting hand on the bottom of their library.

That summary wouldn't pass Azorius scrutiny.

This is Magic: The Gathering, the game we all love for its complexity. The mulligan rules are complicated, but the details are important. Here's the full text of rule 103.5:

Each player draws a number of cards equal to their starting hand size, which is normally seven. (Some effects can modify a player's starting hand size.) A player who is dissatisfied with their initial hand may take a mulligan. First, the starting player declares whether they will take a mulligan. Then each other player in turn order does the same. Once each player has made a declaration, all players who decided to take mulligans do so at the same time. To take a mulligan a player shuffles the cards in their hand back into their library, draws a new hand of cards equal to their starting hand size, then puts a number of those cards equal to the number of times that player has taken a mulligan on the bottom of their library in any order. Once a player chooses not to take a mulligan, the remaining cards become that player's opening hand, and that player may not take any further mulligans. This process is then repeated until no player takes a mulligan. A player can take mulligans until their opening hand would be zero cards, after which, they may not take further mulligans.

Isperia approves.

The full text of the rule is a lot to process, and this guide breaks it all down into sections. Before exploring those sections, there's one more important detail to consider: the "free" mulligan.

This concept is codified in rule 103.5e for the benefit of Commander and other socially-minded Magic formats.

In a multiplayer game and in any Brawl game, the first mulligan a player takes doesn't count toward the number of cards that player will put on the bottom of their library, or the number of mulligans that player may take. Subsequent mulligans are counted toward those numbers as normal.

This rule exists in the interest of preventing non-games, and gets its own section later in this guide.

This section walks through the mulligan process one step at a time.

Each player draws a number of cards equal to their starting hand size, which is normally seven. A player who is dissatisfied with their initial hand may take a mulligan.

Can a player who is satisfied with their initial hand take a mulligan anyway? If they did, how would their opponents know?

Absurd mulligan conspiracy aside, this is where the mulligan process starts in earnest.

First, the starting player declares whether they will take a mulligan. Then each other player in turn order does the same. Once each player has made a declaration, all players who decided to take mulligans do so at the same time.

Mulligans happen after the players determine turn order. This is strategically important in two-player games, because the first player doesn't draw on their first turn. In multiplayer formats, like Commander, every player draws on their first turn, so the sequence has less strategic impact.

To take a mulligan a player shuffles the cards in their hand back into their library, draws a new hand of cards equal to their starting hand size,...

Shuffle the unsatisfactory hand back into the deck, draw another seven. Simple enough. The next step is a minor mulligan tripping hazard.

then puts a number of those cards equal to the number of times that player has taken a mulligan on the bottom of their library in any order.

Except for a free multiplayer mulligan, every mulligan counts, and players must start the game with fewer cards in hand. For every mulligan that counts, the player puts one card from their hand on the bottom of their library. These cards can be placed in any order, which occasionally matters.

Grenzo players love this rule.

Once a player chooses not to take a mulligan, the remaining cards become that player's opening hand, and that player may not take any further mulligans. This process is then repeated until no player takes a mulligan.

At some point, each player should commit to playing a hand. Until that point, players wash, rinse, and repeat the process of declaring a mulligan and shuffling away unwanted hands.

A player can take mulligans until their opening hand would be zero cards, after which, they may not take further mulligans.

Conventional Magic wisdom is to never mulligan to a hand with fewer than five cards. It might be legal to mulligan to zero, but it's not a recipe for success.

Rule 103.5e supersedes the normal mulligan process. Here it is again for reference:

In a multiplayer game and in any Brawl game, the first mulligan a player takes doesn't count toward the number of cards that player will put on the bottom of their library, or the number of mulligans that player may take. Subsequent mulligans are counted toward those numbers as normal.

We commonly refer to this as a free mulligan. The free mulligan rule affords Commander players two chances to keep a full hand of seven. After the free mulligan, every other mulligan counts normally.

Or does it?

In some play groups, mulligans are flexible like the justice system on New Capenna.

Many Commander players or playgroups ignore the official mulligan rules, and allow unlimited mulligans in their games. There are some solid arguments in favor of unlimited mulligans, and some strong reasons to follow the rules as written.

Common justifications for gratuitous mulligans include the social nature of Commander, and game balance. We want everyone to have a good time, and a good game starts with a good hand. We also want Commander games to be balanced, and balance is easier to achieve if everyone has a playable first seven.

All other things being equal, these are great reasons to set the official rules aside and focus on having fun.

On the other hand, many players  prefer to abide by the official mulligan rules. The game is fair when everyone plays by the rules. The case in favor of following the mulligan rules has two main points. The rules encourage honest deck building, and honest gameplay.

Unlimited freedom to craft a favorable starting hand leads some players to build decks with mana bases that wouldn't be sustainable in a strict mulligan setting. Especially bad actors exploit unlimited mulligans to search for specific game pieces.

Each player should decide for themselves what sort of mulligan climate they are comfortable with. Note that the examples above are extremes. There are plenty of other ways to moderate mulligans, and this guide discusses some of them in later sections.

Self-contained playgroups will ideally self-regulate to a mulligan norm that works for them. In public venues, playing by the rules promotes a level playing field among strangers.

What does a good or bad starting hand look like? Why should you mulligan? When should you keep a hand that looks bad? These questions and more simmer under the surface of every new game of Magic. Whether through instinct or intellect, players develop their own mulligan habits.

Let's look at some key strategic points to consider in every starting hand.

Keep commanders and companions in mind with all of these keys. Any card the deck can always access is an important consideration before declaring a mulligan.

Curve

The mana curve of an opening hand should scale to the mana curve of the deck.

This hand has a good curve.

The hand pictured above is from a Longshot, Rebel BowmanLongshot, Rebel Bowman deck. There are spells for two, three, and four mana. With four lands, this hand curves out. In a vacuum, it's a great hand.

Considering the deck's commander, and the 92 other cards in the deck, this first seven would not be ideal. More on that later.

Color

An opening hand needs the right color production, or the ability to fix colors.

This hand can fix colors.

Check out this hand from the Dominaria United (DMC) Painbow preconstructed deck. This hand could cast the deck's commander, Jared CarthalionJared Carthalion, on turn five. That's pretty good for a two-land hand.

Is it good enough to keep? We'll discuss that further in sequencing.

Plan

Turn planning starts with the first hand. Even a hand that makes enough mana of the right colors can be a bad hand if the cards don't advance the game plan.

This is a hand with a plan.

This prospective hand comes from a deck with Vhal, Candlekeep ResearcherVhal, Candlekeep Researcher and Cultist of the AbsoluteCultist of the Absolute as commanders. There's enough mana to cast all the spells and both commanders. More importantly, Retrofitter FoundryRetrofitter Foundry can make tokens to sacrifice for Cultist of the Absolute.

This hand isn't without problems. Tainted StrikeTainted Strike and Mirage MirrorMirage Mirror are both situational. They might be dead cards. Is that okay to keep? It's time to talk about sequencing.

Sequencing

Curve, color, and plan all contribute to the hand's sequence. A hand with good sequencing can intentionally pursue the deck's goals in the first few turns.

Of those three example hands, only one of them is a keeper. Let's look at them again.

This hand has a good curve, but a bad sequence for its commander.

The Longshot, Rebel Bowman deck wants to chain low-cost noncreature spells and refill its hand. There's only one noncreature spell in the hand, and the other cards are all payoffs with no gas. Mulligan.

This hand can fix colors, but it's short on lands.

The Painbow hand could cast Obsidian ObeliskObsidian Obelisk on turn two, Faeburrow ElderFaeburrow Elder on three, and Transguild CourierTransguild Courier on four to play the commander out on five. That's a sequence, but it's also a house of cards built on three nonland permanents.

It's a tempting gamble, but the safe play is to mulligan for more lands.

This is a hand with a plan, and sequences nicely.

The starting hand for Vhal + Cultist deck makes the needed colors, plays ahead of curve, and plans to win. Retrofitter FoundryRetrofitter Foundry comes down on turn one, the Ebony FlyEbony Fly on two, Vhal on three, and Cultist of the Absolute on four.

In just four turns, the deck presents a threat with some flexibility and resilience.

Keep hands like this.

Unless...

Interaction

Unless a proactive sequence isn't enough. Sometimes we need removal or protection in our starting hand. Maybe someone else is playing a kill-on-sight commander. Maybe we plan to be the archenemy and we know we'll need protection.

Interaction is another axis to consider when deciding to mulligan. Look around the table and decide if the hand needs to be proactive or reactive.

Ultimately no starting hand can do it all; it's only seven cards. But considering curve, color, plan, sequence and interaction will lead to better mulligans and better games.

Historically, Magic's mulligans bear the names of locations for the premier events where the rules were implemented. The current system is called the London Mulligan after Mythic Championship London in 2019. Rules for the previous iterations are in the glossary of the comprehensive rules. Both of these systems were retired by popular demand.

Paris Mulligan

Using the Paris mulligan, a player who took a mulligan shuffled their hand into their library and drew one fewer card.

Vancouver Mulligan

Using the Vancouver mulligan, a player who took a mulligan shuffled their hand into their library and drew one fewer card. After choosing to not mulligan, a player who took a mulligan looked at the top card of their library and could put it on the bottom of their library.

The Gis mulligan is a favorite among Commander's old guard. It was named after the judge who invented it, Gis Hoogendijk.

Sheldon Menery told the origin of the Gis mulligan on Discord.

Using the Gis mulligan, the player exiles their unwanted hand instead of shuffling it into their deck. The player then draws a fresh seven cards. This may be repeated until the player has an acceptable hand. Then the player shuffles all the exiled cards back into their library.

Here's two mulligan alternatives to try with your play group, and the first one appears on a real Magic card.

Backup PlanBackup Plan allows a player to draw two hands and choose one to keep, and they can still mulligan that hand.

Another potential house rule is loosely inspired by BrainstormBrainstorm. Every player draws ten cards, and places three back on top of the library. While the card quantities may vary, the goal is smoother starts with fewer shuffles. A traditional mulligan can still be used to supplement the Brainstorm approach.

If these methods don't work for your group, you could always make up your own. Who knows, maybe it will catch on?