Facebook says it will work with independent companies like Nielsen and comScore to review more of its metrics after it uncovered new problems with the data it provides to advertisers and publishers that use its network.
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Facebook had apologized to advertisers in September for errors that led to overstating how long users watched videos.
On Wednesday, the Menlo Park, California, company said in a post that it miscalculated four metrics, including undercounting how many people watched all of a video and overcounting how much time people spent reading "Instant Articles," which loads stories from publishers like The New York Times and Washington Post more quickly on Facebook.
Facebook and Google together account for the majority of digital ad dollars spent in the U.S.