Amazon, Google and Wish have removed neo-Nazi and white-supremacist products being sold on their platforms following an investigation by BBC Click.
White-supremacist flags, neo-Nazi books and Ku Klux Klan merchandise were all available for sale.
Algorithms on Amazon and Wish also recommended other white-supremacist items.
All three companies told the BBC that racist products were prohibited on their platforms.
Oren Segal from the Anti-Defamation League (ADL), an anti-hate organisation, said the companies needed to "constantly be on top of what the algorithm is recommending".
He said algorithms had to be "taught to be responsible".
One of the items found for sale on Amazon was a white-supremacist flag featuring a Celtic Cross.
The ADL said the image featured on the flag was "one of the most common white-supremacist symbols"
One shopper had left a "review" of the product in June, stating: "This is a neo-Nazi flag. Amazon should not be profiting from this."
However, another reviewer said the flag would be "good for use in parades" and thanked Amazon for "making it happen".
Amazon's algorithms recommended another controversial flag that shoppers had "frequently bought together".
Both symbols were worn by the Christchurch gunman when he killed 51 people in 2019.
Other products featuring a burning rainbow flag, similar to the one used by the LGBT community, were also found on Amazon.
All of these products have now been taken down by Amazon.
Online retailer Wish has also taken down Ku Klux Klan-themed products, after being contacted by the BBC.
On the page for a KKK-themed cartoon, Wish recommended "related items" including a hood and a Celtic Cross.
Products related to the Boogaloo movement were also found for sale on Amazon, Google and Wish.
The Boogaloo group is a far-right libertarian militia in the US. Several people linking themselves to the group have been charged with terrorism offences, and the murder of state officials in the US.
All three platforms removed the Boogaloo content after being contacted by the BBC.
Google also removed racist content from its Google Books and Google Play stores.
The think tank Demos has raised concerns that online algorithms can push shoppers towards hateful content.
"It often takes human investigation to work out that people are being led down this path," said Josh Smith of Demos.
How have the companies responded?
Amazon told the BBC: "The products in question are no longer available and we've taken action on the bad actors that offered the products and violated our policies."
Google told the BBC: "We don't allow ads or products that are sold on our platforms that display shocking content or promote hatred. We enforce these policies vigorously and take action when we determine they are breached."
Wish said: "We are working hard to remove these items and taking additional steps to prevent such items appearing again."