Google used to be the main source of referral traffic for web publishers. Then eclipsed it.

And now, is back on top again.

Over the course of 2017, the search engine has become publishers' main source of external page views, according to new data from Parse.ly, a digital analytics company.

It's basically a flip from the beginning of the year: In January, Facebook provided nearly 40 percent of publishers' external traffic; now that's down to 26 percent. And Google, which started the year at 34 percent, now generates 44 percent of traffic. Parse.ly's data comes from some 2,500 publishers that use its analytics service, including the Wall Street Journal, Time Inc., Mashable and Huffington Post.