Vinted users have been reacting angrily following a change that caused items being listed as the wrong size.
The popular resale platform has updated its measurement guidelines for women's and children's clothes without notifying all shoppers about the modification.
Many shoppers and sellers are posting online stating that platform listings now display a modified sizing category than originally posted as a result of the reclassification.
The company said the revised method more closely matches comparable marketplaces.
It has advised users to check their listings and update the measurements by hand if necessary, resulting in member annoyance.
Previously, the sizes had both a single numeric size and a letter, for instance S/8 or M/10.
The new system has an alphabetical indicator and numerical range such as S/UK 8-10.
With some products, the measurements have been reclassified - such as a large size was previously a 12 but currently displays as UK 16-18.
Frankie Bridger, who makes TikTok content about plus-size fashion, explained the modification "makes transactions more difficult".
"Not many brands say XL is a 20-22," which is what Vinted now does.
Another user, from Glasgow, stated items she posted with size 14 tags were displaying on the service as size 20–22.
"If anyone [who is] size 20-22 buys them they're going to be very disappointed," she said.
Charlotte Lunn, located in England, said she had been left angered due to the update requiring manual adjustment the sizing for "all her products".
"This situation is especially annoying, as I'm chronically ill and platform income has been essential after experiencing income reduction," she stated.
The platform boasts over 100 million members, with 18 million British users.
It has emerged as a preferred choice compared to resale services such as eBay and Depop.
This represents another occasion where an unanticipated change to the app has proved unpopular: previously, the service retracted a modification concerning shipment methods due to shopper criticism.
Elena Hartwell is a tech enthusiast and lifestyle writer exploring the intersection of innovation and well-being.