The new Edge logo. (Microsoft Image)

As of today, Microsoft’s default web browser is officially shifting to an open-source engine best known for powering a rival browser.

Let that sink in for a second, and you’ll get a sense for just how much the tech world has turned upside down in the last decade.

A little more than a year after announcing the plan, Microsoft on Wednesday morning released its reborn Edge browser for Windows and Mac, rebuilt on the open-source Chromium project — the same underlying technology that powers Google’s rival Chrome browser.

How did this happen? For starters, no one was testing with Microsoft’s browser. That’s a generalization, of course. Some developers were, in fact, checking their sites for compatibility and bugs in Microsoft Edge. But the successor to the once-dominant Internet Explorer wasn’t a natural part of many standard testing routines.

Desktop browser market share, via NetMarketShare.

This was due in part to the fact that Edge, the default browser for Windows 10, wasn’t available on older Windows versions or the Mac. But it also spoke to the growth of Chrome and Firefox over the past decade. And the lack of testing resulted in just enough compatibility problems and user frustration that Microsoft ultimately deemed the situation unacceptable.

That’s the word from inside the company, and it explains how Microsoft came to announce a decision that would have been almost unthinkable in years past.

Compatibility is expected to improve measurably as a result. In practical terms, the biggest impact promises to be on Windows users currently using Chrome. The move should make it easier for those users to switch to Edge, with the ability to run Chrome-based extensions and quickly migrate saved passwords, favorites and other settings from an existing Chrome installation.

But bigger picture, Microsoft’s strategy shows just how much the browser market and the broader tech landscape have changed since Internet Explorer ruled the early days of the web. Web browsers, after all, were so competitive that Internet Explorer was a central battleground of Microsoft’s landmark U.S. antitrust case.

With the new Edge release, Microsoft is choosing to compete not on the underlying engine but instead on higher-end features, such as the ability to annotate PDFs in Edge, and query a corporate intranet from the search experience, among other features designed for businesses.

Edge also offers advanced privacy capabilities, and a new Internet Explorer mode for better compatibility with older sites and apps. The company is hoping that the trade-off in adopting an open-source will lead to greater adoption and retention of users for its other products and services, including Microsoft Bing, enterprise management technologies and other products.

The new Edge is generally available now as a manual download, and it will roll out via Windows Update in the weeks ahead.

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