Chrome is challenging Microsoft's Internet Explorer as the world's most-used desktop browser, having passed Firefox, according to new data collected by Statcounter, which samples the browser-agent string used of thousands of sites.

The data for the "world" region on StatCounter for the month so far shows IE just ahead, at 32.42% against Chrome's 32.29%. That share varies by day as well, because a number of people use IE at work and then Chrome at home.

Update: StatCounter has asked us to clarify: while StatCounter's weekly stats show Chrome passing IE on a worldwide basis (and fluctuating a great deal if you look at weekends, when Chrome tends to get a "bounce"), the data here are based on the data for the month so far. Weekly (and daily) data can fluctuate a great deal depending on events, which is why we prefer to take a longer sample.

It's a remarkable triumph for Google's browser, which was only launched in September 2008 - and attests both to its quality and, arguably, the benefits of being advertised on the front page of the world's most-visited search engine, where a "Download Chrome" button marked the only time the company has advertised any product rather than a charitable offering such as blood donation (as it did after the US 9/11 attacks in September 2011 2001).

Chrome is one of a new generation of browsers, conceived from the ground up to be both more stable and more secure than those which preceded it. Thus for example every separate tab or window runs as a separate process which can be killed individually; and if one of them crashes, it won't bring the other tabs/windows down. (This can make it memory-hungry, but on modern desktops and laptops that's not a significant constraint.) It has also proven to be very secure, surviving its first two years at the Pwn2own contest - although this year it was the target of focussed attention by "grey hat" hackers who found and exploited flaws. (Google fixed them soon after.)

But while the headline figure is straightforward, once you start to dig into the figures the story becomes more intriguing.

Here's the world map, country by country, drawn from the StatCounter data. IE is blue; Firefox is brown; Chrome is green. All the data relates to the month so far and shows only the leading browser for each country, no matter how narrow the lead - so in that sense this gives you an overview that's rather like "first past the post" voting. No, it's not perfectly representative. But it's indicative. It's also only for this month, up to 21 May, so it's the freshest snapshot we can get.

(Thanks to Pete Warden's wonderful OpenHeatMap for letting us render this map. Go to the site and buy one of his books, why not.) You can also view this map directly on OpenHeatMap.

You might expect that Chrome would enjoy its strongest position, and have taken the lead, in the US - since that is after all Google's home.

In fact, according to Statcounter, IE is the leader in the US and Canada. On reflection, that makes sense, since those countries will have the largest and oldest installed base of PCs, and those are most likely to be corporate, and locked down to using IE.

In fact the "regional" breakdown according to StatCounter for May is as follows:

Worldwide: IE 32.4%, just ahead of Chrome 32.3%; Firefox 25.4%,

Africa: Firefox 40.6%, Chrome 29.9%, IE 23.6%

North America: IE 38.3%, Chrome 25.3%, Firefox 21.9%. (It's also the only region with an appreciable Safari usage, at 12.5%.)

South America: Chrome 49.4%, IE 26.6%, Firefox 21.4%

Europe: Firefox 30.7%, Chrome 29.4%, IE 28.5% (the closest three-way fight)

Asia: Chrome 37.6%, IE 32.5%, Firefox 24.3%

Oceania (Australia/Pacific): IE 34.9%, Chrome 25.5%, Firefox 22.5%.

Antarctica: Firefox 75.1%, IE 15.6%, Chrome 5.8%

Statcounter does IP detection so that it knows where a browser request originates - so if someone from China, say, is browsing a page in Germany, that counts as a Chinese request, not a German one.

In fact the highest regional share for Chrome is found in Asia, although Russian's adoption won't have hurt either.

In Europe as a region, Chrome is second, after (surprise!) Firefox. But here again there are variations. In the UK - which is Google's largest market outside the US (more than $1bn revenues per quarter), IE still holds sway, 36% to Chrome's 28% (but ahead of Firefox at just under 20%). In countries such as Germany and France, it's Firefox.

Conclusions? I'm going to go back and do a historical comparison to see how Chrome has risen, but the obvious conclusion seems to be the countries which have the newest installations of PCs, and which have the least in terms of legacy installations or reliance on burnt-in IE products (hello, ActiveX) which do best.

Quite probably Chrome will pass IE for world share by the end of this month. For Google, that's a benefit: it gets data from users about what they're searching for and where they're going. Butin return users get a fast, secure browser which is being constantly updated and for which Google has a cross-platform plan to integrate it with its Android OS.

Special update for Opera lovers: if you zoom in on the map, you'll find that Ukraine is the only country where Opera is the most-used browser. I don't know why it hasn't coloured it differently, sorry, But you'll find its value is different from the surrounding countries.