Shein may have the fast-fashion market cornered, but a growing number of its customers are calling for increased accountability from the company as indie designers continue to accuse it of ripping off their work.

As the most-installed shopping app in America, Shein has become an e-commerce giant, one that's particularly popular with Generation Z.

But its growth has not been without controversy. In addition to the steep environmental cost associated with fast fashion, Shein is also routinely criticized for copying designs from indie designers.

The designer behind Elexiay, a Black-owned fashion brand, said on Twitter last week that Shein had copied the design of its Amelia top, a crochet sweater that's handmade in Nigeria and costs $330. Shein's offering, mass-produced in the nearly identical color scheme, was sold for $17 until it was removed from the website.

"Spent hours designing and brainstorming this design and it takes days to crochet each sweater. It's quite disheartening to see my hard work reduced to a machine made copy," the designer wrote on Twitter.

It's a sentiment other creators have echoed. Reclamare PH, another crochet designer, said on Instagram that Shein had copied one of its pieces and asked followers to boycott the company. The designer behind Sincerely RIA, a brand inspired by Fulani culture, tweeted last month that Shein had copied the design of a dress and had even "[stolen] the brand's aesthetic."

It's not just clothes. Artists have reported having their original works reproduced without permission, as have designers who create enamel pins and earrings.

Shein did not respond to multiple requests for comment. A marketing agency that works with the brand also did not return requests for comment.

Copies are often legal in the fashion world

When it comes to fashion, copyright law can leave little protection for creators.

For starters, the law doesn't allow companies to copyright "useful things, at least not in their entirety," Julie Zerbo, the lawyer and journalist behind The Fashion Law blog, told NPR.

Generally speaking, that means a designer is unable to claim broad protections for articles of clothing that serve a basic function. For example, designers could not claim protection for any and all sweaters simply because they happen to make sweaters. But they can copyright the creative aspects of their work that make it different from the norm, such as a unique pattern. If it sounds confusing, that's because it is — even for the professionals.

"And so, [with] a dress, a shoe, a bag, copyright law forces a brand that wants to claim protection to show the creative elements of this larger garment and separate them out," Zerbo said. "It makes for a pretty messy and not straightforward reality. The reality is, in most cases, it's perfectly legal to knock off a dress design."

It's in this gray area that fast-fashion brands often thrive. Zerbo said they often copy "just enough" so that the final result is recognizable without copying anything that's trademarked or otherwise legally protected.

"They do a pretty good job of walking that line," Zerbo said. "And that allows them to operate in this space doing exactly what it is that they're meant to do, which is take other trends that are on the runway or elsewhere and reproduce them at a lower cost."

Indie brands still have some options

Still, indie brands aren't completely without options. Sending a cease-and-desist letter is a go-to move, and the brands can also work to reach an agreement outside of court; these settlements can involve the offending companies agreeing to pull the pieces from their store and paying the original designer a monetary settlement, Zerbo said.

It's a polarizing topic: Some commenters are staunch defenders of Shein, arguing that the average shopper can't be expected to spend hundreds on a single garment when a vastly cheaper option is available.

In the meantime, indie designers still have Twitter, Instagram and other platforms to raise awareness, which critics of Shein said can lead to more customers for the original creators as well as increased demands for change.

It may already be working: On TikTok, the "boycottShein" hashtag has been viewed upward of 3 million times. Since big brands rely on online popularity to stay relevant, indie designers and their supporters are hoping hashtags could be an underdog's most powerful weapon.