An infamous online debate has reignited after an optical illusion that left social media users dumbfounded.

The black and blue vs white and gold dress debate, which went viral in February 2015, caused a sensation across the globe following a post on social media. The garment appeared to be a plain bodycon number, but due to baffling lighting in an uploaded image of it, it sparked a fierce reaction with people seeing it as either blue and black or white and gold.

Internet users were split into factions over the dress’s true colours, sparking viral hashtags #blackandblue and #whiteandgold, and turning the dress into a cultural phenomenon that even drew the attention of researchers.

The conversation began when Alana MacInnes, of Uist, and Caitlin McNeill, from Colonsay, sought opinion on Tumblr about the dress’s colouration. Ms MacInnes captured the shot of the notorious dress, whereas Ms McNeill escalated the argument to viral heights by asking online: “Guys please help me – is this dress white and gold, or blue and black? Me and my friends can’t agree and we are freaking… out.”

Instead of a simple consensus, what ensued was a global frenzy. The discussion took fashion bloggers, major news outlets including the BBC, Buzzfeed, the Washington Post, Wired magazine, and even celebrities by storm as they joined the heated discourse.

On X, previously Twitter, the topic trended via multiple hashtags, with #TheDress becoming particularly dominant. Academics offered their scientific take to demystify the visual illusion, while stars didn’t shy away from weighing in with their perspectives.

American actress and writer Mindy Kaling sparked a debate when she tweeted: “IT’S A BLUE AND BLACK DRESS!” Academy Award-winning actress Julianne Moore responded: “@mindykaling @bjnovak what’s the matter with you guys, it’s white and gold”. Taylor Swift also joined in, tweeting she saw the dress as blue and black and confessed to feeling “confused and scared”, her post was retweeted 111,134 times and liked 154,188 times.

The dress even has its own detailed Wikipedia page. The debate has now been reignited thanks to a video on TikTok. The video, posted by creator @aizyer, explains why the dress appears different colours to different people.

In the caption, the TikTok user said: “Reminder that this is an optical illusion and even if you don’t see certain colours, that doesn’t mean other people are wrong. However, the actual colours of the dress are black and blue.”

The video then states if you colour pick it, you get the “colours gold and a shade of desaturated blue”. The creator added: “It’s important to understand this dress is not in lighting where it can be darkened.”

The dress in the original image is surrounded by “warm and bright colours” with “no sign of heavy lighting besides from the flare from the window behind it”. The video creator explains how the colours around the dress can affect how it’s perceived, with the photo being “overlayed in a warm bright light” responsible for the optical illusion.

They explained: “Many people see gold and white because their mind filters out a darker blue shade rather than a warm light”, and added: “If you still can’t see it, I recommend you look up a video on how to/one that more thoroughly explains this illusion than I did.”

The phenomenon re-sparked the debate in the comments section, with one user claiming: “I cannot physically see black and blue,” and another questioning: “How the hell do people see gold and white?” Another simply stated: “I understand but I still can’t see it.”

What colour do you see? Join the discussion in the comments section.