Through the use of plugins, Shotwell can publish photos and videos to the following services, each of which requires an account:
Flickr
Picasa Web Albums and Google+
YouTube (videos only)
Tumblr (videos only)
Any site running the Piwigo photo gallery software (photos only)
To publish selected photos in a collection, choose
Publishing to Facebook requires you to grant certain permissions to the Shotwell Facebook application. You only need to grant these permissions once, when you first associate Shotwell with your Facebook account.
You will be only able to publish images with at most the permission you granted to the Shotwell Facebook application
Similarly, publishing to Flickr requires you to log in and permit Shotwell Connect to access your account.
If you have a Google account, but have not yet used Picasa Web Albums, you will need to log in to Picasa using a browser once before you can publish to this service.