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 female and kids' apparel but did not contact every member regarding the update.
Countless users and merchants are posting online stating that platform listings now display an altered size classification compared to what was initially listed because of the remapping.
The company said the revised method more closely matches other platforms.
It has advised users to check their listings and update the measurements by hand if necessary, which has left users frustrated.
Before the change, the sizes had both numerical and alphabetical indicators, like S/8 or M/10.
The new system has an alphabetical indicator and numerical range like S/UK 8-10.
With some products, the measurements have been reclassified - like an L measurement used to be a 12 but is now a UK 16-18.
Frankie Bridger, who produces content about larger sizing, stated the update "complicates both purchasing and selling".
"Rarely do manufacturers list XL as sizes 20-22," which is what Vinted now does.
A different member, located in Scotland, explained products she uploaded with size 14 tags were appearing on the platform as larger sizing 20-22.
"Should someone sized 20-22 purchase these they will likely be quite upset," she stated.
Charlotte Lunn, based in Derby, explained she became annoyed due to the update requiring manual adjustment the sizes on "every single listing".
"This situation is especially annoying, since I have chronic health issues and Vinted sales have been crucial following partial earnings loss," she said.
The service features exceeding 100 million members, including 18 million in the UK.
It has proved a popular alternative to second-hand platforms like eBay and Depop.
This represents another occasion that an unexpected update to the app has proved unpopular: previously, the platform withdrew an update concerning shipment methods following member complaints.
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