Unicode provides separate code-points for the Old Cyrillic and civil script forms of this letter.

When Peter I of Russia introduced his "civil script" in 1708, based on more western-looking letter shapes, spelling was simplified as well.

Various Russian alphabet reforms were influential as well, especially Peter the Great's Russian Civil Script of 1708 (the Grazhdanka).

Cyrillic letter-forms were derived from 10th-century Greek, but the modern forms have more closely resembled those in the Latin alphabet since Peter the Great's civil script reform of 1708.

It continued in use in Serbian until the orthographical reforms of Vuk Karadžić, and in Bulgarian (where it also acquired a civil script glyph variant) until the late nineteenth century.

Ksi was eliminated from the Russian alphabet along with psi, omega, and yus in the Civil Script of 1708 (Peter the Great's Grazhdanka), and has also been dropped from other secular languages.