Members of the platform have expressed outrage after an update resulted in products showing incorrect sizing.
The popular resale platform has altered its sizing categories for women's and children's garments but did not contact all shoppers about the modification.
Many shoppers and sellers are posting online stating that platform listings now display a different size category compared to what was initially listed because of the remapping.
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, resulting in member annoyance.
Before the change, the sizing featured numerical and alphabetical indicators, like S/8 or M/10.
The updated approach includes a letter with a size spectrum for example S/UK 8-10.
With some products, the size labels have been reassigned - such as a large size used to be a 12 but now shows as UK 16-18.
Frankie Bridger, who produces content about larger sizing, said the change "makes both selling and buying harder".
"Not many brands say XL is a 20-22," which is what Vinted now does.
A different member, from Glasgow, stated items she posted on Vinted with size 14 labels were showing in the marketplace as size 20–22.
"Should someone sized 20-22 purchase these they may become frustrated," she said.
A different user, located in England, said she had been left angered because the modification necessitated personal updates the sizes on "every single listing".
"Personally, this is quite irritating, because of my ongoing medical condition and Vinted sales have been crucial after experiencing income reduction," she explained.
The platform boasts over 100 million shoppers, with 18 million British users.
It has proved a popular alternative versus similar marketplaces including eBay and Depop.
This represents another occasion where an unanticipated change within the service has received backlash: previously, Vinted reversed a change concerning shipment methods after backlash from users.
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