MacOS 9.0 was released in October 1999 with the final update for it, version 9.2.2, release in December 2001. MacOS 9.2.2 is the last version of MacOS based on the original Macintosh operating system.

This is the MacOS 9 desktop. Over all the user interface is not much different from the MacOS 8.x desktop but there have been many technical improvements and some new features added. (Note, these screen shots also show a useful third party utility called "Dave" that enables Macs to fully participate in a Windows NT network)

The control strip, which was available for earlier versions of MacOS has been improved. You can now simply drag tiles onto the strip to install them, instead of having to put them in "Control Strip Modules." You can now also delete one by holding the Option key, then dragging it out.

Mac OS 9 can, optionally, have multiple users. Each user can have a different desktop theme and sound settings. Users can be given limited permissions so as to prevent them from messing up the Mac while still letting them use it.

With multiple users enabled the above login box appears at startup. Microsoft completely ripped off the appearance of this login window in Windows XP.

This is the multiple user control panel used to add and modify user settings.

A very funky feature of MacOS 9 is that it can use your voiceprint as a password. You record a phrase and when you log in it does not just check the phrase but also that you are the one saying it.

Also on the subject of security, MacOS 9 adds the ability to encrypt files on your hard drive.

A screen shot of MacOS 9 browsing the hard drive to show some of its icons. In 9.0 - 9.0.4, most applications would install to the "Applications" folder. 9.1 changed that, as it shipped at the same time, and along with, Mac OS X 10.0. "Applications" is now used for OS X applications, and "Applications (Mac OS 9) for OS 9 apps. It cannot be renamed to remove the (Mac OS 9).

MacOS 9 ships with Sherlock 2. You can use it to search your hard drive, as well as places on the internet. Google even has a plugin you can install that allows Sherlock to search it.

This version of MacOS also ads a software update feature that can get system software and application updates from Apple over the internet. You can get updates manually or schedule a time to get updates automatically.

It also adds a network browser that enables you browse file servers, web servers and FTP servers.

Also on the subject of networking, MacOS 9 has an improved version of AppleScript that can work remotely over TCP/IP with other Macintoshes.

Not that it is part of MacOS (thank goodness) but a web browser that was once popular for it was Microsoft Internet Explorer 5 for the Mac. Microsoft, however,  has completely abandoned IE for the Mac. This version will run on 9.x but actually can run on MacOS as far back as 8.1 (on PPC only). There is also a MacOS X native version but Microsoft has abandoned that version as well.

The last version of Mozilla that will Run on MacOS 9 is version 1.2.1. Unlike IE, however, Mozilla is still being actively developed for MacOS X.

This is the Quicktime 6 Player, MacOS 9.0 - 9.1 comes with Quicktime 4, and 9.2.1 comes with Quicktime 5. Quicktime is used internally by MacOS for many image, drawing, and sound operations.
 

Logging out of MacOS 9.