Chữ khoa đẩu is a doubtful script supposed to be used in the Hồng Bàng period, which was believed to disappear later during the Chinese domination of Vietnam. However, it is note-worthy that the term "chữ khoa đẩu" itself comes from "tadpole script" (kēdǒu zì) in Chinese texts produced in Vietnam while the ones produced elswhere refers to kēdǒu zì as variants of the ancient Chinese characters.
"Chữ khoa đẩu" is also considered a distinct Muong language script similar to Thai alphabet and Lao alphabet. The script has 30 basic consonant signs. In 2013, a book by Đỗ Văn Xuyền was published in which he claimed to have deciphered "chữ khoa đẩu" used by the Vietnamese ancient. However, Xuyền's claim, like the earlier ones by Bửu Cầm or Lê Trọng Khánh, is lack of scientific basis, and the script is indeed based on the Brahmic scripts used by Tai peoples in Vietnam.