“I was just looking for an answer because it was messing with my head,” said Caitlin McNeill, a 21-year-old singer and guitarist.

Within a half-hour, her post attracted some 500 likes and shares. The photo soon migrated to Buzzfeed and Facebook and Twitter, setting off a social media conflagration that few were able to resist.

As the debate caught fire across the Internet — even scientists could not agree on what was causing the discrepancy — media companies rushed to get articles online. Less than a half-hour after Ms. McNeil’s original Tumblr post, Buzzfeed posted a poll: “What Colors Are This Dress?” As of Friday afternoon, it had been viewed more than 28 million times. (White and gold was winning handily.)

At its peak, more than 670,000 people were simultaneously viewing Buzzfeed’s post. Between that and the rest of Buzzfeed’s blanket coverage of the dress Thursday night, the site easily smashed its previous records for traffic. So did Tumblr.

Everyone, it seems, had an opinion. And everyone was convinced that he, or she, was right.

“I don’t understand this odd dress debate and I feel like it’s a trick somehow,” Taylor Swift wrote on Twitter. “PS it’s OBVIOUSLY BLUE AND BLACK.”

“IT’S A BLUE AND BLACK DRESS!” wrote Mindy Kaling. “ARE YOU KIDDING ME,” she continued, including an unprintable modifier for emphasis.

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