How Offside Technology Works: Cameras, Timing and Referees

Offside technology helps establish positions and timing, but the football law determines what those facts mean. Seeing a line on screen is only one part of understanding a decision. Start with the relevant playing sequence and the distinction between an offside position and an offside offence.

Position alone is not the offence

IFAB's Law 11 distinguishes being in an offside position from committing an offence through involvement in active play. That is why one frozen image cannot answer every offside question. The subsequent involvement and the relevant phase of play matter.

The law also defines which body parts count and the relevant moment when a teammate plays or touches the ball. Consult the version applicable to the competition and season for the exact wording and exceptions. Do not substitute a television line for that rule.

Establish the relevant moment

A position comparison depends on timing. An image selected before or after the relevant touch can produce a different apparent relationship between players. The useful question is how the official system identifies and reviews that moment, not which social-media frame looks most convincing.

Keep the sequence around the touch available where possible. A cropped still can omit the information needed to decide involvement or understand why the officials considered a particular action.

Tracking provides evidence

Semi-automated systems can use player tracking and information that helps identify ball contact. The exact installation varies. Do not assume that every league has the same cameras, sensors or update rates merely because both use an offside graphic.

FIFA's technical explanation is a reference for the arrangements it describes. A detailed equipment claim for another competition should be supported by that competition's documentation. Technology categories are not identical hardware inventories.

Officials still apply the law

The system's positional information does not remove questions about active involvement and the playing sequence. Referees apply the rules to the incident. This is the central distinction between measuring a player's location and deciding that an offence occurred.

Avoid claiming that every call is made solely by an algorithm or solely by one camera operator. The official process needs to be described for the actual competition. A short video can introduce the principle without documenting every implementation.

Read the animation correctly

A reconstructed three-dimensional view is a way to explain the decision. It is not the same as the raw image from an ordinary broadcast camera. Perspective can make a television view misleading for close spatial comparisons.

Ask whether a graphic is an official output or an illustration made by a broadcaster or viewer. A line drawn on a screenshot may communicate an opinion without establishing the system's measured positions or chosen timing.

A practical order for reviewing a disputed call

Identify the competition and applicable law, the relevant teammate's touch, the body parts used in the position comparison and the player's involvement. Then consult any official explanation of the technology and review. If one element is missing, state the uncertainty instead of claiming certainty from the line alone.

This guide and its video explain scope and process rather than report an independent GKN Labs system test. For the separate question of whether the entire ball crossed the goal line, read goal-line technology. Those systems answer different questions and should not be conflated.

Sources and scope

• Official reference 1
• Official reference 2

Related videos

The linked videos use Turkish narration. This article provides the English explanation of the same topic and assumptions.

• Watch the companion video
• Watch companion video 2

Edited by GKN Labs. Editorial update: 4 November 2026. Cover and explanatory visuals are illustrative, not evidence of product testing or measurement.