Microsoft Opens To Third-Party Add-Ins, Microsoft’s web-based email and calendaring client, is now open to third-party developers who want to build tools on top of it. Using the Outlook API, developers can build what Microsoft calls “contextual experiences” for This is clearly part of Microsoft’s overall effort to make the data that its users create in its productivity apps available outside of these tools.


Given that is a web app, it’s no surprise that developers will use HTML, CSS and JavaScript to build their add-ins. Because these add-ins use the same APIs as the extensions for the desktop version of Outlook, the add-ins for will also work there and in the Outlook web app that’s part of Office 365 (which is different from the more consumer-oriented — because there can never be enough confusion about all of the¬†different versions of Outlook).

It looks like Microsoft is going to take a deliberately slow approach to bringing these add-ins to its users, though. This summer, Uber and the email scheduling tool Boomerang will launch their add-ins. With this, Uber will allow you to schedule a ride from the Outlook calendar and Boomerang will bring its smart calendar assistant and email reminders to

Over time, Microsoft will open this feature to more developers, too, but it’s unclear¬†when it plans to do so.

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