Flagstack is a GPS-based game that can be played worldwide for free after registration via the app. Players participate by searching for physical or virtual items on the map, which are tied to specific GPS coordinates. Upon reaching these coordinates, players can collect the items and earn virtual points that are added to their account. The items remain on the map for other players to find, while the collected items are marked as "found" in the player's account.

The game encourages players to accumulate points in order to increase their player level. In the lower levels, fewer points are required to level up, but as players progress, the number of points needed to advance increases.

Flagstack offers an engaging and competitive experience for players who enjoy location-based games. With its worldwide reach and free registration, it provides an accessible platform for players to explore and compete in capturing flags.