Mac OS 9.0

Mac OS 9.0, codenamed "Sonata", is the first release of Mac OS 9, announced by Apple Computer on October 23, 1999. It was promoted by Apple CEO Steve Jobs as the best "internet OS ever" and began shipping the next day. Macintosh clones were no longer officially supported.

Development
Mac OS 9.0 originally began development in early 1999 as Mac OS 8.7.