During our regular reviews to ensure the accuracy of our systems, we recently found and fixed a bug that misattributed some clicks on video carousel ads as link clicks. This bug occurred when people were on mobile web browsers on smartphones — not on desktop or in the Facebook mobile app.

The bug affected billing only for the following conditions: for the video carousel ad unit; when the advertiser chose to bid on link clicks; and only for people who were on smartphone web browsers. In these cases, instead of being billed only for link clicks (clicks to an advertiser’s selected destination), these advertisers were incorrectly billed when people clicked on the videos in the carousel to enlarge and watch them. Advertisers will receive a full credit for the charges they incurred for these misattributed clicks.

Most consumers use Facebook through the app on their phones, and mobile web browser ad impressions make up a small percentage of the overall ads impressions people see on Facebook. Given that this bug related to mobile web for smartphones only, and specifically for video carousel ads that bid on link clicks, the impact from a billing perspective was 0.04% of ads impressions. Regardless of how many impressions were affected, we take all bugs seriously and apologize for any inconvenience this has caused.