Facebook reveals measurement glitch

According to a post on the company’s blog, the bug was found during a regular review to ensure the accuracy of its systems and only occurred when users were on mobile web browsers on smartphones, not on desktop or in the Facebook mobile app. 

Instead of being billed only for link clicks, some advertisers were incorrectly billed when people clicked on the videos in the carousel to enlarge and watch them. Facebook has stated that all affected advertisers will receive a full credit for the charges they incurred for these misattributed clicks. 

Facebook claims that, given the small percentage of people accessing Facebook via a mobile web browser, the impact from a billing perspective was just 0.04% of ad impressions.