[1] Many Buddhist texts taken to China along the Silk Road were written using a version of the Siddhaṃ script.

At the time it was considered important to preserve the pronunciation of mantras, and Chinese was not suitable for writing the sounds of Sanskrit.

Kūkai introduced the Siddhaṃ script to Japan when he returned from China in 806, where he studied Sanskrit with Nalanda-trained monks including one known as Prajñā (Chinese: 般若三藏; pinyin: Bōrě Sāncáng; 734–c. 810).

By the time Kūkai learned this script, the trading and pilgrimage routes over land to India had been closed by the expanding Abbasid Caliphate.

[10] In the middle of the 9th century, China experienced a series of purges of "foreign religions", thus cutting Japan off from the sources of Siddhaṃ texts.

In Japan, the writing of mantras and copying/reading of sutras using the Siddhaṃ script is still practiced in the esoteric schools of Shingon Buddhism and Tendai as well as in the syncretic sect of Shugendō.

In Japan, a special brush called a bokuhitsu (朴筆, Cantonese: pokbat) is used for formal Siddhaṃ calligraphy.

Some efforts have been made to create computer fonts, though to date none of these are capable of reproducing all of the Siddhaṃ conjunct consonants.