On 2017 Dec 14, Your Name wrote
(in article ):

I don't know about Windows, but Mac OS X can have at least four letter
extensions (.tiff, .jpeg, .html for example).

Windows no longer cares how long the extension is. Windows (and, I think, but
I’m not certain macOS) cares only that the entire filename and dot and
extension is 255 characters or less and that certain illegal characters,
notably slashes, are not used. There was a problem where Windows had a max
path of 255 characters, later 260 characters, but Microsoft was pulled
trickery and there’s a path length maximum of 32,767 characters which can
be extended if you really, really, REALLY want to go to a lot of trouble.

I submit that 255 character filenames, including dot and extension, is plenty
for mere mortals, as is a 32,767 character path.

I don’t know what the max path length is on macOS. It appears to exceed
32,767 characters. I haven’t attempted to test that. Have at it.