Microsoft outlined new directions for Windows 10's update model in a pair of blog posts. It looks like the company is shifting its twice-annual major release cycle to a twice-annual major/minor release cycle, with major upgrades in spring and minor upgrades in the fall.

To understand the shift, you need to know a little about how Microsoft has released Windows 10 builds to date—and particularly, how they've released them to Windows Insiders. In short, Fast Ring subscribers are the first to get new features and updates. Slow Ring subscribers get those features before they're public but not until after the Fast Ring folks have had a while to flush out the worst of the bugs.

In the past, this meant Fast Ring customers got a new major Windows 10 build first, then Slow Ring customers got that same build after the first few servicing updates had been applied. What happened this year was different: Fast Ring insiders skipped 19H2 (fall 2019) entirely and went directly to 20H1 (spring 2020), and the Slow Ring never joined them at all.

On July 1, the Slow Ring instead got an ostensibly brand-new build of 19H2, which the Fast Ring had never touched. If you're not already intimately familiar with how Windows 10 preview builds are deployed, it may be easier to follow this in a quick table:

What Insiders expected What Insiders got Spring 2019 Fast Ring gets a new fall 2019 preview build Fast Ring gets a new spring 2020 preview build Summer 2019 Slow Ring gets the fall 2019 build that Fast Ring already tested Slow Ring gets a brand-new fall 2019 preview build

ComputerWorld's Gregg Keizer argues convincingly that this isn't a one-off blip with the 19H2 build but is instead a sea change in how Windows 10 preview builds will be deployed from now on. The key points are that Microsoft isn't describing 19H2 as a fully featured new build at all—and that 19H2 isn't deployed as a full OS replacement. Instead of downloading 19H2 as an entire OS, users on build 1903 (aka the May 2019 Update) can deploy it as a set of patches, much like a Cumulative Update (or like the Service Packs of yore).

When you put all this together, it looks very much like the previously speculated shift to a major/minor release cycle. This would honor the spirit of the agreement with Windows Insiders on the Slow Ring, even if it fudges the letter a bit: Slow Ring insiders aren't getting the Fast Ring's seconds anymore, but they're also not being asked to test major (and potentially breaking) new features.

In another departure, the Slow Ring is now being given new builds and features in trickles rather than all at once. As Microsoft's John Wilcox notes, "we are using a controlled feature rollout (CFR) to gain better feedback on overall build quality, [so Slow Ring subscribers] may not see the new 19H2 features right away."

If Microsoft continues in the vein that it has begun with 20H1 and 19H2, the Fast Ring will get longer periods of time to test the biggest and potentially more problematic major feature upgrades, and the Slow Ring will get the first crack at—and more time to test—the smaller incremental updates aimed at fixing long-term problems in performance and stability.