Known by a few different names over the years, what's now called "Zombie traffic" has started to gain more and more attention in the SEO world as of late, particularly in the last year or so. A massive debate is now taking place on the WebmasterWorld forum on the topic.
The term refers to traffic by a group of organic users coming from Google who behave like zombies; dwelling on the site and slowly browsing from page to page, but not converting. Zombie traffic seems to have a seasonal component, occasionally originating from geographic areas far from the ones relevant to the website.
There are various theories regarding why this behaviour is happening:
- Bots or people from other countries using fake IP addresses for click-fraud purposes may be to behind it. Even though many are adamant that traffic appears to be from active users, the way they navigate the site is not akin to how real users would behave.
- Google is sending traffic (bad traffic in this case as it's unrelated) in order to keep your traffic steady and encourage you to keep PPC campaigns active.
- Your website is identified as transactional at times or as informative at others. This can be applied to eCommerce websites in particular. If your website is recording very low conversions, in fact, it may also mean that you're attracting the wrong type of users. The supporters of this theory also mention algorithm flukes, tests and RankBrain learning as a possible reason.
- The very last theory, connected to the previous one, states that Google knows who is a "likely buyer" and who isn't (based on the user intent of the query, the user search history, the user location and similar factors) and will shift search results based on those types of users, but is sometimes getting it wrong.
John Mueller, who was asked about the phenomenon during a Google Hangout, seemed surprised and said he cannot think of any specific reason for Zombie traffic to exist. So, he has asked webmasters to send him examples for him to look into. From what we know, he has not found any good example yet, since all "Zombie traffic" he analysed in the last few weeks seems to be caused by issues like wrong geo-targeting or poor content.