Shoppers are voicing their frustration following a change that caused listings displaying inaccurate size information.
The popular resale platform has altered its size classifications for female and kids' apparel failing to inform every member regarding the update.
Numerous buyers and vendors are posting online saying Vinted listings now show a different size category than originally posted as a result of the reclassification.
The platform stated the new system was more in line with similar services.
It has advised users to review their products and manually change the size where appropriate, resulting in member annoyance.
Previously, the measurements included numerical and alphabetical indicators, like S/8 or M/10.
The new system has a letter and a range for example S/UK 8-10.
For certain items, the sizing has been recategorised - like an L measurement was previously a 12 but is now a UK 16-18.
A fashion influencer, who creates plus-size fashion videos, stated the update "complicates both purchasing and selling".
"Few clothing companies classify XL as 20-22," which is what Vinted now does.
Another user, based in Glasgow, explained products she uploaded with size 14 tags were displaying on the service as measurements 20-22.
"If buyers measuring 20-22 acquire them they're going to be very disappointed," she said.
Charlotte Lunn, from Derby, stated she felt frustrated due to the update requiring manual adjustment the sizes on "every single listing".
"For me this is particularly frustrating, since I have chronic health issues and platform income has been essential following partial earnings loss," she stated.
The app has more than 100 million users, including 18 million in the UK.
It has proved a popular alternative compared to resale services such as eBay and Depop.
This isn't the first time where an unanticipated change on the platform has faced criticism: earlier, Vinted reversed a change to its shipping options due to shopper criticism.