Since links are so important, it's interesting to analyse which websites have the most links. It's particularly interesting to compare link authority data with our perceptions about which sites are more popular, important on the web.
Below is a table ranking the global top 30 websites according to the number of inbound links they have - particularly those with the greatest number of separate domains linking to them.
Theoretically these should have the highest basic SEO authority in the world. On-page content, social media signals and many other factors also affect rankings. But as the world's leading authority sites it's reasonable to expect that the sites at the top of the list should be able to rank in Google for just about anything.
Did you know that Twitter - not Google - has the highest link authority site on the web?
Some of this data might surprise you...
Microblogging platform and the world's second most popular social network. Many sites link to their Twitter feed
Google's main homepage
Was the biggest search engine before Google's dominance. Now merging with Bing
China's top search engine - China has the world's largest population (more than 4 times more people than USA)
The most popular blogging platform
Google's blogging platform
Online retailer that began life selling books
The most popular video-sharing social network - owned by Google
Microsoft's search engine and rival to Google
Provides Flash for online video and reader software for PDF documents - both are popular and frequently linked to.
A leading consumer-to-consumer marketplace
Microsoft global homepage
China's leading web analytics provider
The leading professional networking website
Chinese search engine
The leading global news provider (US-based)
The world's most popular auction site (peer-to-peer)
The world's most popular peer-to-peer payment system. Websites using PayPal often link to the site
Leading Chinese web portal
Homepage of one of the world's most popular social networking sites
User-edited (wiki) encyclopedia
Yahoo's Japan homepage
A leading blogging platform
China's biggest web portal
Google's Japan homepage
Microsoft Network homepage - used to be the default homepage for Windows computers
Leading provider of news, entertainment and information - ad free - to the UK and the world. Funded by UK TV owners
Domains are listed in strict order of authority - with the highest authority sites at the top. Authority is based primarily on the number of linking domains. 10 links from 10 domains typically represent more SEO value than 10 links all from the same domain.
Perhaps most interesting of all is that based on this data Twitter is the most authoritative site on the web. Perhaps this is in part because many businesses and individuals link to their Twitter feed from their website.
Of course SEO is about much more than just links and domain authority - but link-based metrics are among the most important SEO factors and they do tend to correlate well with rankings. Based on the enormity of Twitter's link authority alone, pages on the Twitter.com domain might be expected to rank far better in Google than they actually do, for a wide range of terms. Do tweets simply not represent enough content to rank well? That seems likely and might explain why Wikipedia tends to rank far better than Twitter. (Could Google actually be suppressing Twitter URLs? I've seen other anecdotal evidence that this may indeed be the case and it may be worthy of further research).
Yahoo! comes third - way ahead of Bing and Facebook - which is also something of a surprise at first. But it's a much older domain. It's been a major part of the web for much longer and at for quite some time was the most popular site on the web.
Baidu coming fourth in the link popularity chart is a reminder that China is the next global superpower - soon to overtake the USA to become the world's richest and most economically active nation. If China is emerging as the most important country in the world then Baidu is also becoming the most important search engine in a global context. It's the fourth highest authority in the world according to this data, and I expect it to rise to the top of the list by 2015.