China’s Shein may be the biggest shopping site you’ve never heard of.

It’s large, fast and purely digital, wading into the territory of more established rivals, like Zara and H&M.

In September alone Shein’s app enjoyed 10.3 million global downloads, according to Sensor Tower data.

That boosted its total to almost 230 million.

To put that into comparison, H&M’s app has just over half of that and Zara less than a third.

At the end of September, Shein was the world’s most downloaded shopping app on iPhones - according to analytics platform App Annie.

So what are some the drivers behind its stealthy success?

Firstly, it’s 100% digital.

Legacy brands have big city center stores, a costly disadvantage in the stay-at-home age.

That gives an edge to online-only retailers like Shein.

Then, there’s its effective social media marketing.

Founded in 2008, it’s aimed squarely at Gen Z.

Harnessing tactics like discount codes and influencers on Instagram and TikTok,

it relies on so-called "brand ambassadors" to garner clicks.

Finally, there’s its core business mantra: shift low-cost, high volume products - fast.

Hundreds of new designs are uploaded to the app every week - with prices around half that of its rivals.

Inditex revolutionized the fashion industry in the 1990s by speeding designs to stores like Zara and Stradivarius using factories close to its headquarters in Spain.

Industry sources say Shein also uses factories close to its HQ in Nanjing.

But whereas Inditex can get designs from drawing board to store in around 3 weeks, Shein’s lead time is just three days - ramping fast fashion up to a whole new gear.

While it’s gaining a huge following, its visibility is limited compared to its rivals.

Shein is privately-owned, and does not share sales data.

Whereas the likes of H&M are keen to show transparency, detailing sourcing and working conditions, Shein gives no details about the manufacture of its products.