What are some alternatives?
When comparing Storie and Riff, you can also consider the following products
Balloon - A drop box for your Dropbox
Hype - Using Hype, you can create beautiful HTML5 web content.
Storyheap - Manage your SnapChat and Instagram stories.
Meld - What is Meld? Meld is a visual diff and merge tool targeted at developers.
Medium API - Official Medium API