Microsoft today confirmed the rumors that have been swirling all week. As part of a sweeping change to one of the flagship components of Windows 10, it will rebuild its Microsoft Edge browser from the ground up, ripping out its proprietary EdgeHTML rendering engine and replacing it with the open-source Chromium code base.

Yes, that Chromium. The same one that's at the heart of archrival Google's Chrome browser.

My colleague Mary Jo Foley has the details here: "Microsoft's Edge to morph into a Chromium-based, cross-platform browser."

It's an extraordinary capitulation from Microsoft, which has spent nearly four years and a staggering amount of engineering effort on a quixotic campaign to convince Windows 10 users to ditch their current browser in favor of Microsoft Edge.

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That effort was doomed to fail, because of a series of strategic mistakes. So what makes Microsoft think that they can convince the world that this all-new Edge is a worthy alternative to Chrome?

Let's start with what went wrong with EdgeHTML. In theory, the idea of building a standards-based rendering engine to compete with Chromium's Blink engine makes perfect sense. After all, who wants a monoculture?

But when that noble idea collided with the real world, guess what happened?

Edge was barely able to compete on its native platform, Windows 10.

One of the best sources for real-world data on browser usage is the U.S. Government's Digital Analytics Program (DAP). I've been tracking those numbers for several years, and six months ago, I noticed a startling fact: Microsoft Edge was falling behind Internet Explorer, the browser that Microsoft had officially stopped developing.

Even as the Windows 10 installed base continued to climb, traffic from Microsoft Edge dropped. Among Windows 10 users, the usage share for Microsoft Edge, as measured by DAP, has been steadily declining. Edge usage dropped from 20.3 percent in the second quarter of 2017 to 19.4 percent in the first three months of 2018.

Also: From 1990s Internet Explorer to Microsoft Edge: Classic Windows browsers TechRepublic

For the three months ending November 30, 2018, that number plunged again, to 17.1 percent. Meanwhile, Google Chrome usage on Windows 10 increased to 58.3 percent.

Remember, Microsoft Edge is the default browser on Windows 10, which means that the first thing most people do with a new Windows 10 device is download Chrome and set it as their default browser.

The Edge upgrade mechanism made the problem even worse.

Microsoft decided early on to deliver updates to Edge as part of its semi-annual Windows 10 feature updates. With each successive update, Edge has been adding features and improving steadily in terms of reliability and security.

But corporate customers are not seeing those improvements. IT managers are notoriously conservative when it comes to Windows 10 deployment, and Microsoft now allows them to postpone feature updates by up to 30 months. So even Windows 10 early adopters are likely stuck with older Edge versions.

Edge was a non-starter on desktop devices not running Windows 10.

When Microsoft first decided to place its chips on EdgeHTML, the company projected that it would have Windows 10 running on a billion devices within two or three years, including a few hundred million Windows phones.

That plan didn't exactly work out.

Meanwhile, for the 15 percent of desktop devices running non-Windows operating systems (mostly MacOS), Microsoft Edge isn't an option at all. That cohort includes a disproportionate number of web developers, making it difficult for them to test their sites on Microsoft's browser.

And for the 40 percent of desktop devices running older (but still supported) Windows versions, Windows 10 isn't an option. Chrome and Internet Explorer are, which explains why those two browsers are doing so well.

Meet the new Edge, same as the old Edge?

Microsoft's plan is to continue using the Microsoft Edge brand, including the bright blue "e" logo, but to rebuild the browser itself using the Chromium open-source project code. A preview release will appear in a few months, but the first official download is still "a year or so" away.

That schedule is a bit awkward, with the promised release for Windows 7 coming only a few months before the official January 2020 end-of-support date for that OS.

Also: When will Microsoft end support for your version of Windows or Office?

Microsoft certainly has the engineering talent to ship a solid Chromium-based Edge, and they won't be hobbled by the need to spend most of their time tweaking the rendering engine to deal with websites that were built and tested exclusively for Chrome.

But there will still be headaches to deal with, chief among them being the availability of extensions. I'm told that the engineering goal is to make it possible for any existing Chrome extension to work unmodified on the new Edge, but that still means developers will have to package those extensions for the Microsoft Store. A non-trivial percentage will probably decide it's not worth the hassle.

The availability of the new Edge on Macs will make it easier for web developers to test their sites on that browser. But whether they will do so is still an open question.

The biggest selling point of the new browser for Microsoft will be privacy. In theory, they can build a browser that is 100 percent compatible with Chrome, without the need to sign in to Google services. In a world where both Facebook and Google are coming under increasing fire for their data-collection practices, that's potentially a winning argument.

Also: Microsoft open sources the inference engine at the heart of its Windows machine-learning platform

Of course, Microsoft has been down that road before with its "Scroogled" campaign, and the results were, to put it charitably, disastrous. Five years later, with the miserable Mark Penn gone from the company and Satya Nadella in the CEO suite, it might work.

But even if the new Edge doesn't help Microsoft increase its browser share substantially, it's still good news for the web at large. Microsoft has already been making impressive contributions to the Chromium codebase, and whatever it does with the new Chromium-based Edge will go back to the community. If some of Edge's innovations make it into other browsers, even Google Chrome, then everyone wins.

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