The Sensing Barrier is a giant, dome-shaped barrier placed over a designated area. The barrier is not visible to the standard eye; when viewed with certain dōjutsu, it can be seen that there is a design of several circles which have the kanji for boundary (界), and barrier (結界, kekkai) inscribed in them. When linked with a Sensing Water Sphere, all unauthorized passage in and out of the barrier can be detected and pinpointed.
In the anime, this barrier is depicted as being very unreliable, as there are a number of instances of foreign shinobi entering the village without being detected at all. An example is when Kazuma entered the village and attacked Sora before he launched his attack on the village, as well as numerous "former" Konoha shinobi re-entering the village as enemies.