🏛️Official — MLBIn Season
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Team Sports
9 players
both
bat, ball
10 essential rules
Baseball is a bat-and-ball sport played between two teams of nine players each. The sport is governed at the professional level in the United States and Canada by Major League Baseball (MLB), whose Official Baseball Rules (OBR) constitute the authoritative ruleset for professional play. The editi...
Per OBR Rule 3.01, the baseball must be a sphere formed by yarn wound around a small core of cork, rubber, or similar material, covered with two stripes of white horsehide or cowhide, tightly stitched together.
Per OBR Rule 3.02(a), the bat shall be a smooth, round stick not more than 2¾ inches (6.985 cm) in diameter at the thickest part and not more than 42 inches (106.68 cm) in length. The bat shall be ...
All fielders, with the exception of the first baseman and catcher, may use a glove or mitt of any weight. OBR Rule 3.05 specifies size limits: Fielder's glove: Not more than 12 inches (30.48 cm) measured from the tip of any finger to the bottom of the glove, and not more than 7¾ inches (19.685 cm...
Per OBR Rule 3.09, batters must wear a protective helmet while at bat, while running the bases, and while in the on-deck circle. Helmets must carry the official approval mark of the Commissioner and must have at least one ear flap (facing the pitcher).
Per OBR Rule 3.03(a), all players on a team shall wear uniforms identical in color, trim, and style. Shoes with pointed spikes similar to track or golf shoes are prohibited (Rule 3.03(b)).
Per OBR Rule 2.01, the playing field is laid out per the Official Baseball Rules diagram. The infield is a 90-foot (27.432 m) square, with bases at each corner.
Per OBR Rule 2.02: Home plate: A 17-inch (43.18 cm) square of whitened rubber, set in the ground so the front edge is even with the rear corner of the batter's box. The sides extending back must be beveled.; First, second, and third base: Must be 15 inches (38.10 cm) square, between 3 and 5 inche...
Per OBR Rule 2.04, the pitcher's plate (rubber) shall be a rectangular slab of whitened rubber, 24 inches (60.96 cm) by 6 inches (15.24 cm). It shall be set in the ground so the front edge is 60 feet, 6 inches (18.44 m) from the rear point of home plate.
Batter's box (Rule 2.05): 4 feet (121.92 cm) wide by 6 feet (182.88 cm) long, located on either side of home plate.; Catcher's box (Rule 2.06): 8 feet (243.84 cm) in length and 43 inches (109.22 cm) wide.; Coaches' boxes (Rule 2.07): Located adjacent to first and third base, each 8 feet (243.84 c...
Per the OBR Definitions of Terms, "Fair Territory" is that part of the playing field within and including the first base and third base lines from home base to the bottom of the playing field fence, and as further determined by the foul lines. "Fo...
A pitcher must retaliate when his batter is hit intentionally
If an opposing pitcher hits your batter in what is perceived as a deliberate or retaliatory manner, your pitcher is expected to hit an opposing batter in turn. This 'eye for an eye' principle is a cornerstone of the unwritten code and is enforced by catchers, veteran pitchers, and managers.
Retaliation is traditionally aimed at an equivalent-value player — ace for ace, star for star. Pitchers who fail to retaliate can lose the respect of their teammates.
Don't peek back at the catcher's signs as a batter
A batter who physically turns his head or otherwise attempts to look at the catcher's pitch signals is considered to be cheating the game's internal code. Catchers who detect a batter peeking will immediately call for a pitch thrown at or near the batter. This is treated as one of the gravest in-game violations.
Distinct from electronic sign-stealing (a written rule violation); this refers specifically to the physical act during an at-bat.
Don't throw at a batter's head, even in retaliation
Within a retaliation culture that accepts hitting batters in the body as an enforcement mechanism, throwing at or near a batter's head crosses a separate, graver line. Even pitchers who embrace the HBP code distinguish between 'sending a message' at the ribs and genuinely endangering a player's life.
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Never mention a no-hitter while it's in progress
Players, coaches, and broadcasters avoid acknowledging an ongoing no-hitter, fearing they will 'jinx' it. Teammates typically isolate the pitcher, refuse to sit near him, and avoid all conversation about the feat until it is over. One of baseball's most universally observed superstitions.
Observed in the dugout of both teams; some broadcasters famously avoided saying the words for entire broadcasts.
Don't admire your home run or flip your bat excessively
A batter who stands at the plate watching a home run, flips his bat dramatically, or trots the bases with deliberate slowness to taunt the pitcher is subject to retaliation — typically an inside pitch or HBP in a future at-bat. This is among the most enforced norms in the game.
The threshold for 'excessive' is culturally contested. Latin American and Korean baseball traditions embrace expressive celebration, creating regular clashes with this norm.
Don't steal bases when your team leads by a wide margin
Stealing bases late in a game when leading by a large margin (commonly cited as 5+ runs) is considered running up the score and disrespecting a beaten opponent. The expected response is for the trailing team's pitcher to hit a batter in retaliation.
The exact run differential and inning threshold are undefined and subjective, making this rule a frequent source of controversy.
Don't bunt to break up a no-hitter
Laying down a bunt solely to end a no-hitter — when you would not otherwise bunt in that situation — is considered a cowardly and disrespectful shortcut. Hitters are expected to earn their hits legitimately. The pitcher who gives up such a bunt-hit has often been viewed with sympathy by fans and peers.
The rule targets opportunistic bunts specifically aimed at the no-hitter, not legitimate sacrifice or squeeze plays.
Keep the home run trot at a respectful pace
Even without a bat flip, a batter who trots the bases dramatically slowly after a home run — lingering to prolong the pitcher's embarrassment — invites retaliation. The trot should be composed and unhurried, not theatrical or deliberately taunting.
Distinct from the bat flip rule; specifically about pace and demeanor during the trot, not what happens at the plate.