Google has released a plug-in that embeds its Chrome browser into rival Microsoft's Internet Explorer, a move one analyst said may be an admission by Google that getting users to switch is harder than it anticipated.

Dubbed Google Chrome Frame, the open-source plug-in can be used with Internet Explorer 6 (IE6), IE7 and the newer IE8, said Google in a blog post introducing the new software.

Google cast Chrome Frame as a way to instantly boost the notoriously slow JavaScript speed of IE, and as an answer to the conundrum facing web developers when designing sites and online applications that rely on internet standards IE doesn't support, such as HTML 5.

"One challenge developers face in using these new technologies is that they are not yet supported by Internet Explorer," said two Chrome engineers and a Chrome product manager on Google's Chromium blog. "Developers can't afford to ignore IE - most people use some version of IE - so they end up spending lots of time implementing workarounds or limiting the functionality of their apps," said Amit Joshi, Alex Russell and Mike Smith, all of Google.

The three were right about IE's popularity: according to the most recent data from metrics firm Net Applications, IE accounted for 67% of all browsers used last month. Mozilla's Firefox, at No. 2, held a 23% share, while Chrome owned just 3% of the market.

Developers can tell IE to flip the switch to Chrome Frame with a single HTML tag on their sites or in their applications' HTML code. Users, however, must install Google Frame manually.

Google portrayed Chrome Frame as a boon to developers and users. "We believe that Google Chrome Frame makes life easier for Web developers as well as users," said Joshi, Russell and Smith. Others speculated that the move might be a way for Google to sneak into systems now running only IE.

However, Sheri McLeish, an analyst with Forrester Research, saw it differently.

"Google's realising that the potential to get people to move off IE is harder than it thought," McLeish said. "Clearly, Google is gunning for Microsoft in all its business, but this is an unexpected path to take for what seemed like an effort on its part to offer a full alternative to IE."

In McLeish's eyes, in fact, Chrome Frame, while good news for developers and even users, is an admission by Google that it won't be able to tempt many IE users, especially those running it within businesses, into switching.

"It might give Google more exposure within an enterprise setting, where it lacks the kind of administrative tools that Microsoft offers for IE," she said, "but what's the motivation for people to migrate to Chrome when they can get some of its benefits within IE? I think its message to get people to migrate is actually decreased. I'm just not sure where Google is going with this."

Google seemed to know. In an entry on the company's Wave developer blog, Lars Rasmussen and Adam Schuck of the Wave team said Chrome Frame was an answer to their prayers.

After noting that IE has fallen behind other browsers in both JavaScript rendering speed and the ability to store web application work offline, Rasmussen and Schuck acknowledged that Google found IE lacking. "The Google Wave team has spent countless hours solely on improving the experience of running Google Wave in Internet Explorer," said Rasmussen, the Wave team manager, and Schuck, the Wave client technical lead.

"We could continue in this fashion, but using Google Chrome Frame instead lets us invest all that engineering time in more features for all our users, without leaving Internet Explorer users behind."