Members of the platform have expressed outrage following a change that caused items being listed as the wrong size.
The second-hand shopping app has revised its measurement guidelines for women's and children's garments but did not contact all shoppers about the modification.
Many shoppers and sellers are posting online saying Vinted listings now show an altered size classification versus the original listing as a result of the reclassification.
Vinted explained the updated approach better aligns with comparable marketplaces.
The platform has recommended to review their products and update the measurements by hand when needed, causing user dissatisfaction.
Previously, the sizes had both a single numeric size and a letter, like S/8 or M/10.
The updated approach includes an alphabetical indicator and numerical range such as S/UK 8-10.
In some cases, the measurements have been reclassified - such as a large size used to be a 12 but now shows as UK 16-18.
Frankie Bridger, who produces content about larger sizing, stated the update "complicates both purchasing and selling".
"Few clothing companies classify XL as 20-22," as the platform currently indicates.
Stephanie Gallen, located in Scotland, said garments she listed on Vinted with size 14 labels were appearing on the platform as size 20–22.
"If anyone [who is] size 20-22 buys them they're going to be very disappointed," she said.
Another shopper, from Derby, said she had been left angered because the modification necessitated personal updates the sizes on "every single listing".
"This situation is especially annoying, as I'm chronically ill and platform income has been essential after experiencing income reduction," she stated.
The service features exceeding 100 million members, with 18 million British users.
It has emerged as a preferred choice versus similar marketplaces including eBay and Depop.
This represents another occasion that an unexpected update on the platform has faced criticism: previously, Vinted reversed a change to its shipping options due to shopper criticism.