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Photos is a new application Apple released replacing the old iPhoto application, from version Mac OS X 10.10.3 onwards.
Apple has stopped updating and supporting iPhoto long time ago. Both iPhoto and Photos looks similar, but they are different applications. Some features of iPhoto are missing in Photos and vice versa.
If you have Mac OS X 10.10.3 or later, then you will have Photos tap. If you would like to learn about Photos app, then you can find tutorials here --> https://help.apple.com/photos/mac/1.2/
To upload photos to websites via Safari, you can do this method. Just click and drag the photos you would like to export, out of Photos app to desktop or a folder in desktop or any location. Then you can upload to those websites from Desktop or from that folder.
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