Microsoft’s plan to fork Internet Explorer into two different web browsers, each with its own rendering engine, is somewhat controversial. But a source is telling me that my initial concerns about that second browser, codenamed Spartan, may be misplaced.

If you listen to the Windows Weekly podcast, you may recall that I wondered aloud about Microsoft’s decision to create this second browser, Spartan, which will come with a new rendering engine forked from the Trident rendering engine used by IE. Why didn’t Microsoft just use this opportunity to adopt the WebKit rendering engine, I asked, and try to innovate with the user experience?

Before we continue, a quick recap: WebKit is a web rendering engine used by Apple’s Safari (on iOS and Mac) and “sort of” used by Google’s Chrome, so between them that’s most of the Internet. In reality, Google has itself forked WebKit into its own web rendering engine called Blink. And while I tend to generalize these things into a single entity (“WebKit”) they are in fact different.

I’ve since heard about what’s happening internally from a source at Microsoft. It’s a single source, and you will rightly accept this information with the understanding that … you never know. But so far this source has been accurate and trustworthy.

First, I was told that my assumption that the IE team hotly debated dumping Trident and adopting WebKit was accurate. In fact, Microsoft allegedly spent several months investigating both WebKit and Blink. Here’s what they found.

Blink is the better choice. It’s technically superior to WebKit, and will be for the foreseeable future.

So why did Microsoft ultimately decide to stick with its own Trident investment and not adopt Blink? Some kind of technical reason? Nostalgia? Old-school IE teammates winning out over the new guys?

Nope.

The reason Microsoft didn’t adopt Blink is simple: Google.

Aside from the obvious issues these two companies have with each other, consider a few other relevant details. Google had split Blink from WebKit earlier because it was always fighting with Apple and wanted control. But now Google is doing what it wants with Blink—as Apple did/does with WebKit—because it’s strategically important to Google. That is, Google could only be counted on to do what was best for Google at all times, and not what was best for Blink generally, and the community of companies using it.

So after examining alternatives like forking Blink and working with Apple on WebKit, Microsoft came back to Trident, I’m told. It decided to fork its own browser rendering engine and, for Spartan, create a version that exorcised the legacy compatibility cruft.

I’m further told that this is a fairly herculean undertaking. But that internally, Microsoft has been happily surprised by the results. My source tells me I’ll be surprised by Spartan and the new engine. And now I’m telling you. 🙂

I guess we’ll see what happens.