The countdown clock to the public release of Windows 10 version 1607, aka the Anniversary Update, is down to just days.
In preparation for that big reveal on August 2, Microsoft last night began delivering the build a few days early to anyone who had signed up for the Windows Insider program and chose the ultra-cautious Release Preview option instead of the Fast or Slow rings.
On the one test system that I had configured for this branch, the upgrade process started shortly after 6 pm Redmond time. The upgrade process itself took about 30 minutes, and the machine in question now shows Version 1607, build 14393.5, on the About screen.
If you're eager to jump to the front of the line, there's still time to enroll your activated Windows 10 PC in the Insider program. You must be running Windows 10 and be signed in with a Microsoft account.
With those prerequisites out of the way, go to Settings > Updates & Security > Windows Update > Advanced Options. There, you can follow the prompts to enroll in the Insider program. Make sure to choose the Release Preview ring (rs1_release) before restarting.
In my experience, it can take up to a day for the update itself to appear, and there's no magic shortcut that will speed up the process. After the update downloads, the installation is straightforward. After the upgrade is complete, you're free to leave the Insider program, although remaining on the Release Preview ring means you're unlikely to see new builds until next year.
I'll have a detailed look at the changes in the Anniversary Update next week.