Members of the platform have expressed outrage after an update resulted in products showing incorrect sizing.
The second-hand shopping app has updated its measurement guidelines for women's and children's garments without notifying all shoppers about the modification.
Countless users and merchants are posting online stating that platform listings now display a modified sizing category compared to what was initially listed as a result of the reclassification.
Vinted explained the revised method more closely matches comparable marketplaces.
They have suggested members to review their products and adjust the sizing manually when needed, which has left users frustrated.
Before the change, the sizing featured numerical and alphabetical indicators, like S/8 or M/10.
The revised method features a letter and a range such as S/UK 8-10.
For certain items, the sizing has been recategorised - such as a large size was previously a 12 but currently displays as UK 16-18.
A fashion influencer, who creates plus-size fashion videos, stated the update "complicates both purchasing and selling".
"Rarely do manufacturers list XL as sizes 20-22," as the platform currently indicates.
A different member, based in Glasgow, explained products she uploaded with size 14 tags were showing in the marketplace as larger sizing 20-22.
"Should someone sized 20-22 purchase these they're going to be very disappointed," she explained.
A different user, from Derby, said she had been left angered 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 Vinted sales have been crucial following partial earnings loss," she stated.
The app has more than 100 million shoppers, including 18 million in the UK.
It has emerged as a preferred choice versus similar marketplaces including eBay and Depop.
This represents another occasion that an unexpected update within the service has received backlash: earlier, the platform withdrew an update to its shipping options due to shopper criticism.
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