Understanding that CMS market share number

You’ll often hear it said that WordPress is the world’s most popular content management system, powering xx% of all websites. But where does that figure come from... and what does it really mean?

WordPress’s share of the CMS market is a continuing good news story for the platform. It’s the centrepiece of many presentations and pitches, as incontrovertible evidence that WordPress should be taken seriously. 50,000,000 Elvis Fans Can’t Be Wrong, right?

The primary source for the headline market share number, the one you hear quoted most frequently, is the rolling study conducted by W3Techs, an independent software consultancy based in Austria.

From a sample set derived initially from Alexa’s list of the top 1 million, then 10 million websites from June 2013, and supported since April 2020 by the Tranco list produced by European academics, they use publicly available information to collate statistics on websites’ usage of technologies and related services.

Sites are analysed ‘approximately once per month’, and data is updated daily. You’ll find plenty of enlightening data free of charge: W3Techs also sends monthly reports running to several hundred pages to paying clients.

Their website isn’t the most user-friendly or intuitive; but it allows you to analyse recent trends, drill into certain details, and combine metrics for some interesting insights.

So for example, I can call up a combined report showing how many websites hosted by major data centre providers use WordPress; or a comparison of recent market share across selected CMS options.

Each site they monitor gets a page of data on their website, listing the technology detected – for example, There are free browser extensions for Chrome and Firefox, which will let you call up this information on demand via a toolbar popup.

The W3Techs team are quite open about the challenges and limitations of their work. Their goal is to be ‘as accurate as one can possibly get’, based on what they can see; and they say with some modesty: ‘We believe that we are not too far away from that goal.’

Having observed them for many years now, I’ll certainly say their numbers have the ring of truth about them, and aren’t subject to the same wild fluctuations seen in certain other sources.

However, the data can sometimes be cited or interpreted incorrectly.

You’ll often hear people quote it as ‘X percent of the internet‘. Of course, there’s much more to the internet than just browsing websites. Strictly, you should say ‘X percent of the top ten or eleven million websites‘ – but it’s surely fair enough to trim that down to ‘X percent of websites‘ in conversation.

But perhaps the most important point to bear in mind, particularly where WordPress is concerned, is that W3Techs do not consider subdomains to be separate websites.

This can produce some initially confusing results: Craigslist clearly isn’t powered by WordPress, but it’s listed as a ‘popular site using WordPress’. You’ll see it stated on its site profile page, though, that WordPress is being used on a subdomain by a secondary site.

I’ve confirmed with W3Techs directly: this means that is counted as a site running WordPress, even though ‘Craigslist proper’ isn’t. But I’m told I shouldn’t expect this to make a big difference: ‘very few of the smaller sites bother to use a subdomain, and even less bother to use more than one CMS for their website.’ (I’d love to see hard data on this, though.)

This also means that the many millions of websites at which do not have a mapped or custom domain applied, all count as a single site.

But since the analysis only covers the top ~10 million sites, and few of these sites still using the free URL generate much traffic, it’s unlikely to be affecting the data to a significant extent.