The Windows 10 Creators Update, due some time in the next couple of months, enables differential updates as part of what Microsoft calls the Unified Update Platform. These updates only contain the changes between one major Windows update and the next, which should make for smaller, faster downloads.
Windows Insiders have been receiving these new differential updates since early December, and Microsoft has reported on the effectiveness of the new scheme. Compared to a “canonical” update (which includes full files rather than just the changed portions), the savings are substantial: the median differential download size of build 15025 was 910MB. The media canonical size of build 15031 was 2.56GB.
This is particularly attractive to members of the Insider program because each new build is delivered as a major update that performs a full in-place Windows 10 install. To take advantage of the differential updates, you’ll have to make sure to never skip any releases; if you’re updating an older build to the very latest, a full download is required. This represents a trade-off on Microsoft’s part: The company doesn’t want to have to maintain a differential update between any and every pair of builds.
Microsoft’s mobile platform has used differential updating for some time. The drawback is that upgrading from an old version to a new version requires the installation of multiple updates, one for each version. Switching to UUP addresses this annoyance; since UUP retrieves a canonical update in this situation, updating is always a one-shot operation.
Because the differential update technology is part of the Creators Update, regular (non-Insider) users of Windows 10 won’t see the benefit until the next major Windows 10 update. Codenamed “Redstone 3,” it is currently due for later this year.
Regular users aren’t going to see differences quite as substantial as the 910MB to 2.56GB difference seen for Insiders, with Microsoft estimating a 35-percent decrease over the canonical download in general. The closer two builds are, the fewer the differences between them will be, and hence the smaller the differential update. Insiders see builds that are sometimes only a few days apart, so they can get very small downloads indeed. Users of the stable channel, in contrast, will always have many months between their builds, and therefore a much larger proportion of the files will change.