Members of the platform have expressed outrage 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 expressing on platforms claiming that product pages now present an altered size classification compared to what was initially listed because of the remapping.
The company said the revised method more closely matches similar services.
It has advised users to check their listings and update the measurements by hand where appropriate, causing user dissatisfaction.
Earlier, the measurements included one number and one letter, for instance S/8 or M/10.
The revised method features a letter with a size spectrum such as S/UK 8-10.
In some cases, the size labels have been reassigned - like an L measurement was formerly size 12 but is now a UK 16-18.
One content creator, who creates plus-size fashion videos, said the change "makes both selling and buying harder".
"Rarely do manufacturers list XL as sizes 20-22," the way the service now categorizes.
A different member, based in Glasgow, stated items she posted featuring size 14 markings were displaying on the service as larger sizing 20-22.
"If buyers measuring 20-22 acquire them they will likely be quite upset," she explained.
A different user, 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, since I have chronic health issues and selling on Vinted has been paramount for me since losing part of my income," she stated.
The app has more than 100 million users, including 18 million in the UK.
It has proved a popular alternative versus similar marketplaces including eBay and Depop.
This is not the initial instance where an unanticipated change on the platform has faced criticism: earlier, the platform withdrew an update to its shipping options after backlash from users.
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