Members of the platform have expressed outrage after an update resulted in items being listed as the wrong size.
This online marketplace has revised its size classifications for female and kids' apparel but did not contact all shoppers about the modification.
Countless users and merchants are expressing on platforms saying Vinted listings now show a modified sizing category than originally posted as a result of the reclassification.
Vinted explained the updated approach better aligns with similar services.
The platform has recommended to examine their items and update the measurements by hand if necessary, resulting in member annoyance.
Earlier, the sizes had both one number and one letter, for instance S/8 or M/10.
The revised method features a letter and a range for example S/UK 8-10.
For certain items, the measurements have been reclassified - such as a large size was previously a 12 but now shows as UK 16-18.
A fashion influencer, who makes TikTok content about plus-size fashion, explained the modification "makes transactions more difficult".
"Rarely do manufacturers list XL as sizes 20-22," which is what Vinted now does.
Another user, located in Scotland, stated items she posted with size 14 tags were appearing on the platform as measurements 20-22.
"If anyone [who is] size 20-22 buys them they're going to be very disappointed," she said.
A different user, 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, as I'm chronically ill and Vinted sales have been crucial for me since losing part of my income," she explained.
The platform boasts over 100 million members, comprising 18 million UK members.
It has proved a popular alternative to second-hand platforms like eBay and Depop.
This represents another occasion that an unexpected update within the service has received backlash: earlier, the platform withdrew an update regarding delivery choices due to shopper criticism.
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