You see the flag go up and the stadium roars — but what exactly does a linesman do? In simple terms, a linesman (often called an assistant referee) watches specific lines and actions to help the main referee keep the game fair. Their calls decide offsides, throw-ins, corner kicks and many tight moments that change results.
This guide gives clear, practical points you can use whether you’re a fan, a coach, or thinking about becoming an official. No jargon, no long rules — just what matters on the pitch and how to read the signals.
In football, the linesman primarily checks offside and signals when the ball goes out. A straight arm points for a throw-in direction; a diagonal arm points to offside; two hands raised if they need the referee’s attention for a substitution or serious incident. In hockey, linesmen handle offsides and many stoppages, while in tennis a linesman calls whether a ball is in or out. Learn those basic signals and you’ll understand a lot of decisions live or on replays.
When you watch a match, notice the flag and the body language. A quick, low flag often means a tight offside; a firm, high flag signals a clear decision. If the assistant runs to the referee, it usually means a serious foul or a goal review request.
Offside is the call fans argue about most. Simple rule: a player is offside if they are nearer to the opponent’s goal line than both the ball and the second-last defender when the ball is played to them. Linesmen judge that moment. VAR now checks some offside calls, but VAR still relies on the original on-pitch flag and timing. That’s why tiny margins and frame-by-frame replays create controversy.
Errors happen — tight angles, fast play, and player movement make split-second calls hard. Good linesmen stay calm, keep their line with the second-last defender, and communicate clearly with the referee. When you see a reversed VAR decision, remember it’s often about a few centimeters on the replay, not a full change of story.
Want to become a linesman? Expect fitness training, regular rules updates, and lots of practice running the line. Most associations require local courses and exams, then graded matches to move up. Being consistent and visible helps — referees trust assistants who are in the right position and decisive.
As a fan, keep this in mind: linesmen don’t decide alone. They’re part of a team trying to get fair results under pressure. Knowing their role makes the game clearer and reduces the “they ruined it” feeling when calls don’t go your way.
During a Sunderland match, a player's comedic reaction to an on-field collision with a linesman became a viral sensation. Amidst the team's successful streak under Régis Le Bris, the player's playful antics highlighted football's entertainment side, much to the delight of fans and social media users.