Vinted users have been reacting angrily due to a modification that led to listings displaying inaccurate size information.
The second-hand shopping app has updated its size classifications for women's and children's clothes failing to inform all users about the change.
Numerous buyers and vendors are posting online claiming that product pages now present an altered size classification than originally posted as a result of the reclassification.
Vinted explained the revised method more closely matches other platforms.
It has advised users to examine their items and manually change the size when needed, causing user dissatisfaction.
Earlier, the sizing featured numerical and alphabetical indicators, such as S/8 or M/10.
The revised method features an alphabetical indicator and numerical range such as S/UK 8-10.
In some cases, the sizing has been recategorised - such as a large size was previously a 12 but currently displays as UK 16-18.
A fashion influencer, who produces content about larger sizing, explained the modification "makes transactions more difficult".
"Not many brands say XL is a 20-22," the way the service now categorizes.
Another user, located in Scotland, explained products she uploaded with size 14 tags were appearing on the platform as size 20–22.
"Should someone sized 20-22 purchase these they're going to be very disappointed," she stated.
A different user, located in England, said she had been left angered because the modification necessitated personal updates the measurements for "each individual item".
"This situation is especially annoying, because of my ongoing medical condition and selling on Vinted has been paramount after experiencing income reduction," she said.
The service features exceeding 100 million users, comprising 18 million UK members.
It has emerged as a preferred choice to second-hand platforms like eBay and Depop.
This is not the initial instance that an unexpected update to the app has proved unpopular: earlier, Vinted reversed a change concerning shipment methods after backlash from users.
A tech journalist with over a decade of experience covering UK innovations and consumer electronics trends.