UI Browser 2.6.1 requires Mac OS X 10.7 (Lion) or later. It has been verified through macOS Sierra 10.12. It recognizes new Accessibility features that Apple has added to macOS over the years.
Older versions of UI Browser are available for older versions of macOS. UI Browser 2.3.0 runs under Mac OS X 10.6 (Snow Leopard), UI Browser 2.1.1 runs under Mac OS X 10.5 (Leopard), and UI Browser 2.0.5 runs under Mac OS X 10.4 (Tiger). UI Browser 1.4.1 for Mac OS X 10.2 (Jaguar) and Mac OS X 10.3 (Panther) is no longer available. Visit Downloads to download these older versions of UI Browser.
Apple's GUI Scripting technology was officially introduced in Panther as a standard feature of Mac OS X. Scripts written using the GUI Scripting technology run on all computers equipped with Panther or newer, but some GUI Scripting features require newer OS versions. (Apple successfully concluded the GUI Scripting public beta test on Jaguar, and the beta version of the underlying GUI Scripting software for Jaguar is no longer publicly available.)