Vinted users have been reacting angrily following a change that caused items being listed as the wrong size.
This online marketplace has revised its size classifications for women's and children's clothes but did not contact all users about the change.
Numerous buyers and vendors are posting online stating that platform listings now display an altered size classification compared to what was initially listed due to the recalibration.
Vinted explained the new system was more in line with comparable marketplaces.
It has advised users to examine their items and adjust the sizing manually where appropriate, causing user dissatisfaction.
Earlier, the sizing featured one number and one letter, like S/8 or M/10.
The new system has a letter and a range like S/UK 8-10.
For certain items, the sizing has been recategorised - such as a large size was formerly size 12 but currently displays as UK 16-18.
Frankie Bridger, who produces content about larger sizing, explained the modification "makes transactions more difficult".
"Rarely do manufacturers list XL as sizes 20-22," as the platform currently indicates.
A different member, based in Glasgow, explained products she uploaded featuring size 14 markings were appearing on the platform as size 20–22.
"If anyone [who is] size 20-22 buys them they're going to be very disappointed," she said.
Another shopper, from Derby, stated she felt frustrated by the change as she had to manually change the sizing for "all her products".
"For me this is particularly frustrating, since I have chronic health issues and selling on Vinted has been paramount after experiencing income reduction," she said.
The app has more than 100 million users, comprising 18 million UK members.
It has become a favored option to second-hand platforms like eBay and Depop.
This isn't the first time where an unanticipated change on the platform has faced criticism: earlier, the platform withdrew an update to its shipping options following member complaints.
Maya Chen is a venture capital analyst with over a decade of experience in tech startups and investment strategy, specializing in emerging markets.