Mozilla will try to squeeze more into Firefox 3.1, the company's chief engineer said today, in part as a reaction to rival browsers from Microsoft and Google.

"Looking at where we are and the competitive browser landscape, we felt we would be doing a better job if we had another four to five weeks," said Mike Shaver, Mozilla's interim vice president of engineering.

Shaver wasn't sure what impact, if any, the additional work would have on Firefox 3.1's final release, which Mozilla had targeted as late in 2008 or early 2009. "It's too early to know what affect it will have," he said. "But that [late 2008, early 2009 timeframe] is still what we're looking at."

In a lengthy post to the mozilla.dev.planning message forum last week, Shaver spelled out what Mozilla hopes to do. There, he listed several features that would benefit from "one more 'feature cycle'" of development, including TraceMonkey, the browser's revamped JavaScript engine, and a privacy mode that was only recently slated for Firefox 3.1.

In an interview, Shaver said the move was in part due to faster-than-expected progress on some features, such as extending TraceMonkey's capabilities into other areas of the Firefox code. "We saw we could apply those [TraceMonkey] techniques to performance in other areas, like DOM [Document Object Model]. We think if we could bang on this a little longer we would get more out of this," he said.

The desire to push TraceMonkey development wasn't a reaction to Chrome, the beta browser Google released two weeks ago. "That's not a reactive thing, it's just the next logical step," Shaver said, noting that Mozilla started work on TraceMonkey more than two months before Google announced Chrome.

But Shaver acknowledged that some of the extra work Mozilla would like to put into Firefox 3.1 is because of competitive pressure. "We're not blind to the competitive landscape," he said. "We're watching other browsers as much as they're watching us."

He cited Mozilla's plans for a Firefox privacy mode as an example. Both Microsoft Corp.'s Internet Explorer 8 (IE8), currently in beta, and Google's Chrome have tools that limit or eliminate what those browsers record during their travels.

"There's a difference between when just one browser has a feature and when it's in several," said Shaver. "There are user expectations."