It should be noted that previous Windows 10 releases did include the new Chromium-based Edge browser, but it was installed alongside the legacy Edge browser.
Also, in order to use the new Chromium-based browser, you had to make the conscious choice to open the new browser. Your legacy Edge browser would open by default.
That changes with the KB4559309 update, which purges the legacy Edge browser. At that point, if you want to use a Microsoft-based browser, your only option will be the new Chromium Edge. Any attempt to open the legacy browser will automatically redirect to the new product.
As part of the update, all of your user data stored in the legacy Edge browser will be ported to the new code. That includes tabs from previous sessions, saved passwords, and bookmarked websites. A small point, but one still worth mentioning, is the fact that unlike previous updates, a system restart is not required to begin making use of the new browser.
If you don’t want to have the new Edge browser installed on your device, you can prevent it. However, doing so requires you to go deep into the system, adding a “DoNotUpdateToEdgeWithChromium” key in your Windows Registry.
That, however, is not a step recommended for anyone except the most experienced Windows users. That is because any time you start playing in the Registry, you run the risk of doing serious damage to the system, so proceed with extreme caution.
On balance, the new Chromium-based Edge browser looks like a good upgrade and the early sense is that most users will be pleased with the change. Stay tuned, because it’s coming soon!