Assistant referees help call offside infractions In football (soccer), assistant referees (also known as linespeople) carry and use flags to signal calls, such as offside, throw-in, and foul, to the main referee. (more) What Is the Offside Rule in Football? soccer Written by Kara Rogers Kara Rogers is the senior editor of biomedical sciences at Encyclopædia Britannica, where she oversees a range of content from medicine and genetics to microorganisms. She joined Britannica in 2006 and... Kara Rogers Fact-checked by Britannica Editors Encyclopaedia Britannica's editors oversee subject areas in which they have extensive knowledge, whether from years of experience gained by working on that content or via study for an advanced degree.... Britannica Editors Last updated May 1, 2026 •History The offside rule in football (soccer) is designed to prevent players from gaining an unfair advantage by positioning themselves too close to the opponent’s goal. A player is considered offside if, at the moment the ball is passed to them, they are closer to the opponent’s goal line than both the ball and the second-to-last defender (the last outfield defender, with the last defender usually being the goalkeeper) are and they are actively involved in...

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