The Facebook News Feed, the centerpiece of the world’s largest social network service, is a streaming series of posts such as photos from friends, updates from family members, advertisements and material from celebrities or other pages that a user has liked.

The test, which is occurring in six smaller countries, now offers two user feeds, according to a statement from the company: one feed focused on friends and family and a second dedicated to the pages that the customer has liked.

The change could force those who run pages, everyone from news outlets to musicians to sports teams, to pay to run advertisements if they want to be seen in the feed that is for friends and family.

The test is taking place in Bolivia, Cambodia, Guatemala, Serbia, Slovakia and Sri Lanka, and it will likely go on for months, Adam Mosseri, the Facebook executive in charge of the News Feed, said in a blog post.

Mosseri said the company has no plans for a global test of the two separate feeds for its 2 billion users.

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Facebook also does not currently plan to force commercial pages “to pay for all their distribution,” he said.

Facebook, based in Menlo Park, Calif., frequently tests changes big and small as it tries to maximize the time people spend scrolling and browsing the network. Sometimes it makes changes permanent, and other times not.

Depending on how people respond, two news feeds could mean that they see fewer links to news stories. News has proved to be a tricky area for Facebook, as hoaxes and false news stories have sometimes spread easily on the network.

The test has already affected website traffic for smaller media outlets in recent days, Slovakian journalist Filip Struhárik wrote over the weekend in a post on Medium.

Publishers might need to buy more Facebook ads to be seen, he wrote: “If you want your Facebook page posts to be seen in old newsfeed, you have to pay.”