It's an OS-wide scripting framework, that a lot of (most) applications running on macOS support. The beauty of it is that it works on top of Apple Events and is layered. An application may inherit a standard set of exposed scripting endpoints and may also implement its own specific set of behaviors.
Even the standard inherited set of endpoints can be extremely powerful due to accessibility functions that are baked into the entire operating system.
Chrome offers both. Firefox offers nothing. Of course applications can additionally offer their own scripting APIs (Chrome has DevTools, I'm sure Firefox has something equivalent) but a major advantage of OSA is its stability and uniformity. It's a hidden treasure for power users and obsessive feedback loop minimizers. Alas, when it comes to regular users, the most Apple managed to do with it was Automator.app, a very constrained experience that did not really take advantage of the underlying power.
Chrome offers both. Firefox offers nothing. Of course applications can additionally offer their own scripting APIs (Chrome has DevTools, I'm sure Firefox has something equivalent) but a major advantage of OSA is its stability and uniformity. It's a hidden treasure for power users and obsessive feedback loop minimizers. Alas, when it comes to regular users, the most Apple managed to do with it was Automator.app, a very constrained experience that did not really take advantage of the underlying power.
https://developer.apple.com/library/archive/documentation/La...