Through the use of plugins, Shotwell can publish photos and videos to the following services, each of which requires an account:
Flickr
Google Photos
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, YouTube or Google Photos requires you to log in and permit Shotwell Connect to access your account.