• by Tobi Elkin  @tobielkin, January 11, 2016

Facebook, through its Facebook Audience Network (FAN), is testing ad placements on mobile Web pages with nearly 10 publishers, according to AdExchanger, which broke the news on Monday.

Previously, FAN dealt only with ad placements in mobile apps. FAN reportedly achieved a $1 billion run rate in Q4, so the addition of mobile Web sites could be a boon.

Social publisher Diply is one of the publishers in the closed beta test, Facebook confirmed via AdExchanger. The move is viewed as an alternative to Google's AdSense.

Facebook's move into mobile Web inventory means that FAN will have access to a new crop of publishers and could pose a challenge for Google, Apple, AOL-owned Millennial Media and other mobile ad network operators.

Facebook's Audience Network launched with the company's acquisition of LiveRail two years ago. Native video was later added to FAN last year.

The expansion into mobile Web sites leaves open the prospect of whether Facebook will over time add desktop media, an area where AdSense is well-entrenched.