Facebook's Instagram has rolled out what it thought was a small-scale test of a new tap-to-advance feature that lets users scroll through posts horizontally.
But the new feature went to more users than it expected, touching off an instant freak-out among Instagram users and leading the social network to swiftly pull the plug on the test.
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Adam Mosseri, whom Facebook recently installed as head of Instagram with the departure of the photo-and-video-sharing app's founders, responded on Thursday to users on Twitter, explaining that the horizontal-scrolling feature was "supposed to be a very small test that went broad by accident. Should be fixed now. If you're still seeing it simply restart the app. Happy holidays!"
The test "went to a few orders of magnitude more people than intended, sorry about that," Mosseri posted on Twitter.
He also tweeted, "Sorry for the confusion! Always trying new ideas, usually with a much smaller number of people."
An Instagram rep blamed a "bug" for the unwelcome appearance of the feature. "Due to a bug, some users saw a change to the way their feed appears today. We quickly fixed the issue and feed is back to normal," the rep said.
Many users who received the Instagram app with the new scrolling feature immediately decried it as a step backward compared with the vertical-feed orientation -- making it harder to see updates and slowing down the ability to navigate through posts.
Instagram - like other popular apps - has faced a backlash in making design changes.
In 2016, it switched users' feeds from chronological to algorithmically sorted presentation; that led to a Change.org petition to keep Instagram chronological signed by 343,000 people (but Instagram did not revert to the previous design).
Also that year, Instagram changed its logo and the New York Times dubbed the ensuing uproar The Great Instagram Logo Freakout of 2016.