Web publishers that have come to count on Facebook (META 0.14%) posts for traffic to articles have seen that traffic plummet, and some are now shifting their focus from print stories to videos.

The moves, which are now under way by viral news leaders such as Upworthy, Elite Daily, and BuzzFeed, are in part a reaction to evolving consumer preferences. In 2015, the average American spent four times as long watching digital video each day as he did four years ago. And Web video is expected to continue to grow in popularity. But the moves can also be seen as another way publishers are being forced to come to terms with Facebook's changing demands as it remakes its News Feed and builds out its advertising platform.

Video is a key area of growth for the social network, and because it has become so important to many online publishers' success, it doesn't have to apply much force to bend their habits to better fit its own growth agenda. 

Sites are reliant on Facebook for traffic
Digiday reported in January that the website Elite Daily -- which tags itself "the voice of generation Y" -- has been rapidly expanding its video team and turning out videos ranging from short, humorous clips to longer documentaries exploring issues facing millennials. Facebook is responsible for some 98% of the site's social traffic, according to the report, so when it tweaks its News Feed, Elite Daily sees big changes. 

Take 2015, for example. As Facebook reportedly changed its algorithm to de-emphasize those posts that are liked or shared by friends -- the mechanism by which articles go viral -- sites like Elite Daily that rely on viral sharing grew worried their referrals could suffer. Elite Daily certainly took a hit, as Digiday reports its traffic was down 38% in December 2015 from January 2015. That's even as it tripled the number of articles it was posting each day, the Digiday report says. 

But videos have reportedly been seeing better traction on the platform, which has publishers making adjustments to favor creating that type of content.

Looking to turn News Feed into your news source
It's no secret why publishers have come to rely so heavily on Facebook to reach their audience. The social network commands a massive user base: More than 1 billion people use Facebook daily.  

Users are also spending more time on the platform. Last July, Facebook reported that the average smartphone user spends more than 46 minutes a day in its mobile apps -- or nearly a quarter of the total time spent using mobile devices. And that's not including time spent in WhatsApp -- just Facebook, Messenger, and Instagram.

So it seems apparent that a growing number of Americans are using the service to read news and commentary beyond posts from their circle of friends.

Facebook's continuing push to develop its Instant Articles platform, which encourages publishers to post stories directly to the platform rather than link back to their own properties in exchange for an extended reach and a share of Facebook-procured ad revenue, further demonstrates its desire to become the primary source of news for its users. Another key benefit for Instant Articles is that they load more quickly for readers.

And the multiple News Feed format Facebook is now experimenting with will give users options to tailor their feeds so they can access even more content and spend more time with the social network each day. While it's still in testing, the new format is expected to allow users to set up customized feeds based on their interests, like sports, travel, food, or fitness. 

Video is a key growth area
Facebook is looking to continue gaining traction in video, as it looks to take on the Web's video standard bearer, YouTube. It has good reason: Digital video advertising in the U.S. is expected to nearly double from 2015 to 2019, when it is estimated to be a $14.4 billion market, according to eMarketer. For perspective, in 2013, just $3.8 billion was spent on digital video ads in the United States.

And market research has shown that online video advertising appeals to business with marketing money to spend. A BrightRoll survey last February showed that nearly three-quarters of marketers found online video ads as effective or more so than their ads that appeared on television.

The global market for online video ads is expected to reach $19 billion by next year, according to IHS. That provides a sizable runway for growth for a company like Facebook, which is expected to bring in some $17.5 billion in revenue worldwide in 2015.

What's more, IHS expects that about half of online video ad spending by 2019 will be in mobile, where Facebook truly excels.

In a report last May, IHS recognized Facebook's increasingly dominant position in the market, noting that Facebook has "one of the strongest video strategies both in terms of content and monetization."

As it continues to ramp up its efforts in video, users should expect to start seeing more of them in their News Feeds, and publishers who rely on Facebook posts for traffic should expect to devote more resources to producing video over print.