It is based on American Sign Language, with local admixture in different cities.
Although presented as a coherent language when advocating for recognition by the Indonesian government and use in education, the varieties used in different cities may not be mutually intelligible.
Specifically, the only study to have investigated this, Isma (2012),[2] found that the sign languages of Jakarta and Yogyakarta are related but distinct languages, that they remain 65% lexically cognate but are grammatically distinct and apparently diverging.
Word order in Yogyakarta tends to be verb-final (SOV), whereas in Jakarta it tends to be verb-medial (SVO) when either noun phrase could be subject or object, and free otherwise.
Rather than sign language, education currently uses a form of manually-coded Indonesian known as Sistem Isyarat Bahasa Indonesia (SIBI).