Trail orienteers must identify, in the terrain and in the presence of decoys, control points shown on the map.

[2] TrailO has been developed to offer everyone, including people with limited mobility, a chance to participate in a meaningful orienteering competition.

Because control points are identified from a distance, and competitors are not allowed to leave the trails, participants with and without physical disabilities compete on level terms.

There are three official competition formats in World Trail Orienteering Championships: PreO, TempO and relay.

Competitors are allowed to move along the trail to observe, but need to choose the answer at the decision point.

The flags are labelled from the left to the right, using the NATO phonetic alphabet (alpha, bravo, charlie, delta, echo, foxtrot).

A night course is similar to a normal PreO course except that reflective markers are used on control point flags.

How far a flag must be placed off the correct location for a control to be considered as zero answer (zero tolerance) is a highly debated topic.

Before the competition, the name, number and class is filled, and the start and finish times are marked like in traditional orienteering.