If you've recently seen posts or ads claiming that Trader Joe's is giving away $750 gift cards, you're not alone. But the viral claim is rooted in a scam, prompting warnings about falling for it.

For example, it might offer $316 for a $400 Target gift card, which works out to a 21% cost. The maximum gift card balance is $500. Company fees start at 8%, but no maximum is specified.