Members of the platform have expressed outrage after an update resulted in products showing incorrect sizing.
This online marketplace has altered its sizing categories for women's and children's garments without notifying all shoppers about the modification.
Many shoppers and sellers are posting online claiming that product pages now present an altered size classification versus the original listing as a result of the reclassification.
The company said the new system was more in line with other platforms.
The platform has recommended to examine their items and manually change the size where appropriate, which has left users frustrated.
Before the change, the sizes had both numerical and alphabetical indicators, such as S/8 or M/10.
The updated approach includes an alphabetical indicator and numerical range like S/UK 8-10.
With some products, the measurements have been reclassified - such as a large size used to be a 12 but is now a UK 16-18.
A fashion influencer, who creates plus-size fashion videos, stated the update "complicates both purchasing and selling".
"Few clothing companies classify XL as 20-22," which is what Vinted now does.
A different member, based in Glasgow, explained products she uploaded featuring size 14 markings were displaying on the service as size 20–22.
"Should someone sized 20-22 purchase these they may become frustrated," she explained.
Charlotte Lunn, from Derby, said she had been left angered because the modification necessitated personal updates the measurements for "each individual item".
"Personally, this is quite irritating, as I'm chronically ill and platform income has been essential after experiencing income reduction," she stated.
The app has more than 100 million members, 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 within the service has received backlash: earlier, the service retracted a modification regarding delivery choices following member complaints.
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