The exact search engine ranking algorithms are a mystery, even for search professionals. We know for example that there are more than 200 ranking factors in the Google algorithm, but the exact mix remains unknown, as Google is anxious to not disclose the details.
The annually report from Searchmetrics about the ranking factors is considered one of the most reliable, as it is based on a huge amount of data. This year the company analyzed 10,000 keywords, 300,000 page titles, descriptions and URLs and 5.3 billion backlinks, generating a total of 150GB of data. The SEO ranking factors for 2013 according to Searchmetrics, are the following:
It is interesting that among the first positions are mostly social signals. That highlights the importance of a social media strategy for good and extensive SEO results. Backlink factors also remain strong, followed by HTML and keyword factors.
The charts including the specific factors for every individual category show also interesting results:
For technical SEO, the main factors are the URL length, the position of keywords in titles and that the URL is not a subdomain.
For on-page content, the main factors are the HTML length, the number of internal links and the number of images.
For backlinks, the main factors are the number of backlinks, the SEO visibility of the backlinking URLs and the proportion of no-follow links.
Finally, for social signals, the main factor is the overall Facebook performance, followed by the Facebook shares and Google +1s.
Of course, do not forget that this report is based on correlation. It displays the main factors for the top ranking websites, but cannot guarantee that they are actually used by Google or that they affect the rankings of every website. The best SEO strategy for every website is to experiment with different tactics, measure the results and continuously optimize.