Vinted users have been reacting angrily due to a modification that led to items being listed as the wrong size.
The second-hand shopping app has updated its measurement guidelines for women's and children's garments failing to inform all shoppers about the modification.
Numerous buyers and vendors have taken to social media saying Vinted listings now show an altered size classification compared to what was initially listed because of the remapping.
The company said the updated approach better aligns with other platforms.
They have suggested members to examine their items and update the measurements by hand when needed, causing user dissatisfaction.
Previously, the sizing featured a single numeric size and a letter, for instance S/8 or M/10.
The new system has an alphabetical indicator and numerical range like S/UK 8-10.
With some products, the size labels have been reassigned - such as a large size was formerly size 12 but is now a UK 16-18.
A fashion influencer, who makes TikTok content about plus-size fashion, stated the update "complicates both purchasing and selling".
"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 displaying on the service as larger sizing 20-22.
"Should someone sized 20-22 purchase these they will likely be quite upset," she explained.
A different user, located in England, explained she became annoyed due to the update requiring manual adjustment the sizing for "all her products".
"Personally, this is quite irritating, because of my ongoing medical condition and Vinted sales have been crucial after experiencing income reduction," she stated.
The app has more than 100 million shoppers, with 18 million British users.
It has proved a popular alternative to second-hand platforms like eBay and Depop.
This represents another occasion where an unanticipated change on the platform has faced criticism: previously, the platform withdrew an update to its shipping options following member complaints.
Maya Chen is a tech journalist and lifestyle blogger with over a decade of experience covering digital trends and cultural shifts.
