The web metrics company said Chrome increased its share by 0.4 of a percentage point, ending the month with a 3.6 percent share. Firefox, meanwhile, grew by 0.3 of a percentage point, finishing October with 24 percent.
Google's browser is closing on Apple's Safari for the Number 3 spot, which is behind Microsoft's Internet Explorer (IE) and Firefox. If the trend from the past three months continues, Chrome will surpass Safari in February 2010.
Firefox, Chrome, and to a lesser extent Safari, all gained ground thanks to another downturn by IE in October. IE's share fell by one percentage point to put it at 64.7 percent. Microsoft's browser has lost three percentage points in the last three months, and nine points in the last year.
Chrome's increase of 0.4 of a percentage point was its largest since Google launched the Windows-only browser in September 2008. In the last three months, Chrome has gained one percentage point, or 62 percent as much as Firefox has increased in the same time.
Safari, meanwhile, grew only slightly, while Opera Software's Opera lost share last month. Apple's browser ended the month at 4.4 percent, up just 0.2 of a percentage point; Opera dropped to 2.17 percent, losing 0.02 of a point.
Both browsers appear destined to be also-rans in the market share race. With the vast bulk of Safari's users on Macs - Safari for Windows accounted for less than a third of a percentage point last month - Apple's browser gains are directly linked to Mac sales, and that platform's performance, percentage-wise, against the dominant Windows operating system .
Both Microsoft and Mozilla again made strides in moving users to their newest browsers.
The eight-year-old IE6 lost 1.1 percentage points, dropping to 23.2 percent, while 2007's IE7 lost 1.2 points, falling to 18.2 percent. The new IE8, on the other hand, gained 1.3 percentage points to post an October average of 18.1, another record for that browser. As recently as May, IE8 accounted for just 6 percent of all browsers.
When IE8's compatibility mode - a feature that lets it properly render pages designed for older editions - is taken into account, Microsoft's newest browser accounted for a 20.4 percent share, putting it ahead of IE7 for the first time.
Assuming current trends continue, IE8 will pass the aged IE6 before the end of the year, making good on a Microsoft campaign to get users off its eldest browser. IE6, said Microsoft's manager of Internet Explorer in August, should be abandoned by users able to pick their browser.
Mozilla has also had success in migrating its users to Firefox 3.5, the upgrade launched last June, although the pace has slowed.
In October, Firefox 3.5 increased its share by 1.3 percentage points to 13.9%, dramatically less than the 3.8-point surge in September. Firefox 3.0 slipped 0.8 of a percentage point to end at 8.8 percent.
Firefox 3.0 users face the retirement of their browser in January 2010, when Mozilla will stop serving up security updates for the 18-month-old application. Before then, Mozilla should have wrapped up Firefox 3.6, a minor upgrade that made it to beta last Friday.
Net Applications measures browser usage by tracking the machines that visit the 40,000 sites it monitors for clients, which results in a pool of about 160 million unique visitors per month.