The company actually added Office Insider access earlier this month, but publicized it only today: On Jan. 5, an update to Microsoft AutoUpdate (MAU) for Mac -- Office's integrated maintenance utility -- exposed the Insider program to customers.
To become an Office Insider, Mac users must check the "Join the Office Insider program to get early access to new releases" box in MAU. Users can pull up MAU by selecting "Check for Updates" from any Office application's Help menu.
On multiple Macs used by Computerworld staffers, no new builds appeared when MAU sniffed for updates after the "Join" box was checked, indicating that while the program may be live for consumers on OS X, previews have not yet been generated.
A message on a Microsoft support forum confirmed that. "We're just laying the groundwork for the Mac Office Insider program and getting people signed up," wrote a Microsoft worker identified as "Anneliese" a week ago. "We haven't started releasing Office Insider updates yet."
She pointed to a page on Microsoft's site that described the January changes for Mac Insiders. The build, which will be tagged as 15.18, will include, among other new features, a full-screen mode in the Outlook email client that lets users simultaneously view a pair of messages side by side.
The most recent Office Insider beta for Windows desktop users -- labeled 16.0.6366.2062 -- was released yesterday.
Like the better-known Windows Insider, Office Insider serves as a feedback source for Microsoft's developers, and its participants as guinea pigs for commercial customers.
Employees who have rights to Office 2016 through their company's Office 365 subscription are not eligible to join Office Insider. Instead, corporate administrators may register for what Microsoft calls "First Release," the upgrade track that receives new features before any other. Those roll-outs begin only after the same builds have been tested by subscribers to the consumer-grade Office 365 plans.