Shoppers are voicing their frustration due to a modification that led to listings displaying inaccurate size information.
The second-hand shopping app has altered its size classifications for female and kids' apparel but did not contact all users about the change.
Many shoppers and sellers are posting online saying Vinted listings now show an altered size classification versus the original listing due to the recalibration.
The company said the new system was more in line with similar services.
They have suggested members to examine their items and update the measurements by hand when needed, resulting in member annoyance.
Before the change, the sizing featured a single numeric size and a letter, for instance S/8 or M/10.
The updated approach includes an alphabetical indicator and numerical range such as S/UK 8-10.
With some products, the sizing has been recategorised - such as a large size was formerly size 12 but is now a UK 16-18.
One content creator, who makes TikTok content about plus-size fashion, 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, from Glasgow, explained products she uploaded with size 14 tags were displaying on the service as larger sizing 20-22.
"Should someone sized 20-22 purchase these they're going to be very disappointed," she said.
Another shopper, located in England, explained she became annoyed due to the update requiring manual adjustment the measurements for "each individual item".
"This situation is especially annoying, since I have chronic health issues and Vinted sales have been crucial after experiencing income reduction," she stated.
The app has more than 100 million users, with 18 million British users.
It has become a favored option versus similar marketplaces including eBay and Depop.
This isn't the first time where an unanticipated change within the service has received backlash: last year, the service retracted a modification to its shipping options due to shopper criticism.
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