The two most widely used Web browsers are getting updates, and for once both contenders — Microsoft’s Internet Explorer 9, released Monday, and Mozilla Firefox 4, due Tuesday but available now in “release candidate” form — are competing to offer less.

That’s “less” as in less time spent waiting for the browser to work its way through a complex, interactive page, and less distraction from the interface surrounding that page. In other words, IE 9 (for Windows Vista and 7) and the open-source Firefox 4 (for Win 2000 and newer, Mac OS X 10.5 and newer, and most versions of Linux) both show the effect Google’s Chrome has had on the market.

Chrome’s speed made it my default browser on slow netbooks, on which earlier versions of Firefox and IE could visibly lag. IE 9 and Firefox 4’s “RC” version exhibited none of that slowdown; IE even beat Chrome in one test of its ability to run Web scripts, a core component of the Web applications that we spend an increasing amount of time using. (IE 9 can warn also which plug-ins and toolbars slow down your performance and offer to remove them.)

Chrome remains faster overall. But the performance penalty to use IE or Firefox instead has dropped to the point where most people are unlikely to notice.

Veteran users of each browser will, however, notice their minimalist interfaces.

Microsoft has compacted the top of IE’s window, fusing its address and search boxes into one field (as in Chrome) and then moving the tab icons that represent open pages into the space to its right. That leaves almost the entirety of IE’s window to display the page, but it also makes it difficult to see what pages are in other open tabs.

Its combined address/search bar looks cramped, too, because it holds search, refresh and stop icons that don’t disappear when they’re not relevant. On too many sites, it also pops up a fourth icon, a broken-page “compatibility view” button that you can click to have IE 9 properly display pages designed for older versions of IE.

That last icon’s appearance also undercuts IE 9’s notably improved support for Web standards. This might not make much difference on your desktop today, but when developers don’t have to waste as much time working around IE-specific quirks as they design future sites, we’ll all benefit.

Firefox 4’s looks don’t offer such a radical departure as IE’s new interface, keeping page tabs and core browsing controls — such as the address box, search box and forward and back buttons — on separate lines. That’s the same design as Chrome and Apple’s Safari.

Privacy is part of the pitch for IE 9 and Firefox 4. Both try to help users stop Web sites from monitoring what they do elsewhere on the Web, a concept that’s been called “do not track.”

IE 9 offers two ways to do that, one hidden and the other outright clandestine. If you select a sub-menu of the safety menu available under a gear icon in its top right corner, you can enable a “tracking protection list” of sites that the browser can then stop from tracking your use through such technologies as saving cookie files to your computer. Or you can add a special, empty tracking protection list to activate a feature added just before IE 9 shipped: the ability to tell every site you visit not to track you.

Sites don’t have to honor that request. Firefox 4 spells that out by labeling this option (under the advanced category of its preferences or options window, not privacy as you might expect) “Tell Web sites I do not want to be tracked.” But as political pressure increases, sites might feel obliged to pay attention.

Firefox 4 brings one other improvement to the table: the ability to sync your bookmarks, browsing history, saved passwords and even currently open pages across computers and smartphones. I sent that data (encrypted on Mozilla’s servers) from a Mac release of Firefox to a Windows version, and then to the Firefox Home browsing-assistant app on an iPhone and a beta version of Firefox’s upcoming Android browser.

Both IE 9 and Firefox 4 look like major, welcome advances. But each falls short of Chrome in one key aspect: security. Although Google’s browser automatically updates two major security risks — the plug-ins used to display Adobe Flash multimedia and Portable Document Format file — IE doesn’t even warn you that you’re running out-of-date, unsafe versions. Firefox 4 can, but it’s up to you to install updates. (Note that on a Mac, it still can’t display PDFs by itself.)

Now that these two developers have moved to catch up to Chrome on performance, it’s time for them to renew the competition in security.