Many of Apple’s own apps, such as
Safari and iPhoto, now have a Share menu that allows you to send photos and files to your friends using
Messages, or to upload them to social media sites such as Facebook and Twitter. There’s also a Share option built into the Finder too, allowing you to Command-Click on a file and share it right from your Mac desktop.
Yosemite extends the Share menu by using extensions to add other apps and social sites to the menu. Any social media service can provide a Share extension of its own, and it will then be added to the Share menu so that you can share files and information online. Look in the Extensions preferences panel and you’ll see the standard set of extensions for the likes of Twitter and Facebook, but – with an eye on the huge Chinese market – Apple has included its own extensions for Chinese video-sharing services such as Youku and Tudou.
There are also some great third-party apps that provide Share extensions, such as Pocket, which allows you to quickly copy web pages, photos and other files straight into Pocket and view them offline later on. The handy file-sharing service CloudApp has a sharing extension too, so you can upload and share files right from the desktop by Command-clicking on the file and using the Share menu in the Finder.
Read about Safari extensions here:
The best Extensions for Safari on the Mac