During Build and Ignite 2015, we announced the preview refresh of File Handler add-ins. This add-in type allows developers to create their own custom viewers and editors for non-Microsoft file types in SharePoint Online, OneDrive for Business, and Outlook Web App.
We are pleased to announce that this feature is now generally available 100% in SharePoint Online and OneDrive for Business, and is rolled out to 50% of all Exchange Online tenants. The feature is currently rolling out to additional Exchange tenants and should be available to everyone in the next few weeks.
This Ignite talk is a detailed tutorial on building your own file handlers, but to get started quickly you can: