Pages app in mac has a long list of fonts. Can I use these fonts on my web page by specifying font-family="xyz"?
What I want to know is the fonts used in mac apps like pages,numbers
are proprietary and unique or they are common fonts that will be available and supported on most devices?
The safest approach will always be to use a web font from google fonts or a font that you have directly in your website so browsers can download it always directly from the website. If you just call for a font that is installed in the pc like Times New Roman (that both windows and mac generally have) the website probably will work on both windows and mac, but on linux clients it probably won't work, you can do that but you need to set a fallback font just in case they client doesn't have that specific font.
And when you add mobile to the list it gets even worst, generally android has sans droid, or some other propriatary fonts that PCs just don't have unless they are directly installed.
And even IF the browser tried to make up for the lack of font, it might apply a font that doesn't work too well with your website and end up making some pretty weird formatting issues, and if the OS itself has a font with the same type family and it just applies that one you could end up with the same problem, but generally it probably will just show up all as squares/rectangles.