Members of the platform have expressed outrage due to a modification that led to products showing incorrect sizing.
The second-hand shopping app has updated its size classifications for women's and children's clothes without notifying all users about the change.
Numerous buyers and vendors are expressing on platforms saying Vinted listings now show a modified sizing category compared to what was initially listed because of the remapping.
The platform stated the new system was more in line with comparable marketplaces.
The platform has recommended to check their listings and adjust the sizing manually if necessary, resulting in member annoyance.
Earlier, the measurements included numerical and alphabetical indicators, for instance S/8 or M/10.
The new system has an alphabetical indicator and numerical range such as S/UK 8-10.
In some cases, the size labels have been reassigned - such as a large size was formerly size 12 but now shows as UK 16-18.
A fashion influencer, who creates plus-size fashion videos, explained the modification "makes transactions more difficult".
"Not many brands say XL is a 20-22," the way the service now categorizes.
A different member, based in Glasgow, said garments she listed on Vinted with size 14 labels were displaying on the service as measurements 20-22.
"Should someone sized 20-22 purchase these they may become frustrated," she said.
Another shopper, located in England, said she had been left angered due to the update requiring manual adjustment the sizes on "every single listing".
"Personally, this is quite irritating, as I'm chronically ill and Vinted sales have been crucial following partial earnings loss," she explained.
The app has more than 100 million shoppers, including 18 million in the UK.
It has proved a popular alternative versus similar marketplaces including eBay and Depop.
This is not the initial instance where an unanticipated change to the app has proved unpopular: last year, Vinted reversed a change concerning shipment methods following member complaints.
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