Online marketplaces: what you need to know before you buy

Online marketplaces are booming – 95% of UK consumers made a purchase from one, and around four in 10 of us use them at least once a month.

Amazon and eBay are still the biggest players, but new platforms such as Temu have exploded in popularity and high street retailers like B&Q and Tesco are also getting in on the act.

While these platforms offer convenience and unrivalled choice for consumers – as well as big opportunities for small businesses – there are potential issues that shoppers and sellers need to be aware of.

Read more about how to shop safely online with our in-depth guide.

What is an online marketplace?

An online marketplace is a website that connects shoppers with third-party sellers. eBay might be the most well known – where individuals can use the platform either to shop themselves or to list products for sale – but increasingly we've seen small and large businesses setting up 'shops' on online marketplaces as an alternative to their own site or selling through traditional retailers.

Unlike traditional retailers, online marketplaces are not directly responsible for the products sold through their platforms – that responsibility lies with the third-party seller.

Most popular online marketplaces

Nearly three-quarters of UK marketplace shoppers told us they used eBay*. The site is popular with small businesses, private traders and second-hand sellers; most items are sold through auction, but others are ‘buy it now’. 

Almost two-thirds had shopped on Amazon. The e-commerce giant is a hybrid marketplace: it offers its own products as well as those from other companies, and it hosts third-party sellers, which includes everyone from global brands to private sellers. Some Amazon sellers manage their own shipping and returns, while others outsource their order fulfilment to the platform.

A third of shoppers had bought something from Etsy, which bills itself as a platform for custom-made items, vintage goods and craft supplies. 

Around one in 10 people had used the Chinese site AliExpress, which is known for its rock-bottom prices and became popular during the pandemic. Most of its sellers are Chinese manufacturers and wholesalers who ship products from China. 

New online marketplaces taking the UK by storm

Temu launched in 2022, but has quickly become one of the world’s most popular shopping apps, thanks to its cheap prices and marketing tactics. Shoppers can earn credits if they share referral links or codes and get others to sign up. 

The Chinese site also gamifies shopping: users can collect credits and coupons by playing in-app games. Most sellers are based in China and Temu handles shipping and returns.

Meanwhile, Tiktok, the Chinese social media giant, has reinvented ‘social shopping’ by allowing users with 1,000 followers to earn a commission by plugging products, and by simplifying the purchasing process while you're watching promotional videos. TikTok sellers often lure in users with shopping-channel-style live videos and flash sales.

• Find out more about Temu and TikTok Shop – from how they work to how they offer rock-bottom prices.

High street retailers with online marketplaces

More and more traditional retailers are now adopting a marketplace model. It’s easy to see the appeal: hosting third-party sellers allows a retailer to rapidly expand its range of products with minimal overheads, and it takes a cut of every sale. 

B&Q, Debenhams, Superdrug, The Range and Mountain Warehouse have introduced marketplaces. Even Tesco has launched an online marketplace, which already offers over 200,000 products from third-party sellers.

Home improvement store B&Q has more than 1.2m products from more than 1,100 sellers and has expanded its range to include cookware and tableware. 

The department store chain Debenhams was resurrected as an online-only shop after it went into liquidation in 2020. Owned by fast-fashion firm Boohoo, Debenhams.com now lists 10,000 brands, ranging from little-known homeware retailers to luxury fashion houses such as Armani and Yves Saint Laurent.

Health and beauty store Superdrug has 22,000 products from marketplace sellers on its website, from Korean skincare brands to a Hairy Bikers pie maker.

If you buy from a third-party, the delivery charges and returns process often differ from the shop’s standard policies, and the retailer may take no responsibility if there are any issues.

The rise of second-hand marketplaces

Online marketplaces have also made buying and selling second-hand items easier and more popular than ever.

When we asked 1,300 consumers about their experiences of the online second-hand goods market, Vinted was the highest-rated platform for buying, with a customer score of 75%. eBay came in second place with 72%, while Facebook Marketplace was bottom of the list with a score of 66%.

Vinted also took the top spot when it came to selling, with 78%. Preloved was the runner-up with 69%, while eBay, Facebook Marketplace and Gumtree came in joint third place with 66%.

Our survey also revealed that a third of buyers and a fifth of sellers had experienced a scam in the past two years. Typically, buyers reported receiving incorrect goods, no goods at all or even counterfeit goods.

• Find out more: best and worst places to shop second-hand online

Is it safe to shop on online marketplaces?

A Which? survey found that seven in 10 people who buy from online marketplaces are confident the platforms will ensure the safety of products on their sites*. 

However, these sites aren’t legally responsible for products sold through their platforms, so they aren’t held to the same standards as high street or regular online retailers. Which? investigations have repeatedly found dangerous products being sold by third-party sellers, especially unbranded electronics.

A 2024 investigation that found a plug-in heater bought through B&Q Marketplace presented a risk of electric shock, fire and explosion. We've also tested identical-looking models from eBay, Amazon and Wish.com, all of which were unsafe. It's a trend we commonly find with unbranded electronics bought from these platforms.

Our product safety tests have also uncovered hazardous electric heaters sold on TikTok and Temu, unsafe ‘energy-saving boxes’, unreliable carbon monoxide alarms and dangerous baby carriers and slings on marketplaces including AliExpress, Amazon, eBay and Wish.

One in seven marketplace shoppers had an issue with an item bought in the last two years – that’s around 7.2 million consumers who have potentially experienced harm due to products that are faulty, unsafe or scams. For that reason, we advise doing extra research when you're buying from an online marketplace, especially in the case of electronics and healthcare items. And don't be tempted by the low prices.

• Find out more: how we easily listed an illegal product on online marketplaces

How to tell if you’re buying from a marketplace seller

If you’re shopping on a hybrid marketplace, it’s not always obvious whether you’re buying from the retailer or a third party. 

For example, B&Q Marketplace (diy.com) looks like a standard online shop and marketplace items appear next to the retailer’s products. You have to click on a product listing and check to see if it’s ‘sold and shipped by’ B&Q or a third party. 

Other sites make it easier to spot a third-party seller. Superdrug products have a Marketplace badge on the results page, and a prominent label on the product page states ‘proudly sold and shipped by a Superdrug Marketplace seller’.

If you’re unsure whether it’s a marketplace or a regular shopping website, look out for phrases like ‘sold and shipped by’ and ‘sold and delivered by’. Check the delivery charge and returns process for the product you’re interested in – third-party sellers usually handle their own shipping and returns.

What are my consumer rights on an online marketplace?

If you buy from a retailer or trader on a marketplace, your rights are the same as if you’d bought from any other online store, but you might have to deal with the third-party seller.

You have fewer rights if you buy from a private seller. The principle of ‘buyer beware’ applies: the goods must be as they were described, but the seller isn’t obliged to disclose any faults. However, they would be in breach of contract if they took your money but didn’t send you anything, or they misrepresented goods – if a second-hand item were described as new, for example.

Some marketplace sites offer extra protection for sellers and buyers, so it’s worth checking their terms and conditions. If you have an issue with a third-party seller, you may be able to resolve it via the online marketplace or retailer. Check if there’s a built-in dispute resolution centre. 

• Find out more: What are my shopping rights on an online marketplace?

How to shop safely on an online marketplace

• Check the seller. Are they based in the UK? What’s the customer feedback on their other products? If it’s a business, check reviews on sites such as Trustpilot. 
• Be wary of brands you haven’t heard of. Does it exist outside of the platform? Does it have a reputable-looking website, with a contact email and a returns policy? 
• Avoid unbranded electronics. Our investigations have repeatedly found that the cheap electronics flooding online marketplace sites are unsafe. Stick to the brands you trust.
• Look out for fake reviews. Fraudulent reviews have recently been banned under new legislation campaigned for by Which?, but platforms may not have taken action yet. Be suspicious if there are lots of five-star reviews with little detail about reviewers’ experiences.
• Check the delivery details and the seller's refund and returns policy. Shipping times and costs vary hugely for products sent from abroad. Do they offer a full refund for unwanted goods? Would you need to pay the delivery cost if you return it?
• Look for buyer protections. Some marketplace sites, including eBay and Amazon, offer refund guarantees if an item arrives faulty or damaged, or doesn’t turn up at all.  Take our quiz: Do you know how to shop online safely?

• Take our quiz: Do you know how to shop online safely?

Which? calls for greater responsibility for online marketplaces

Which? believes online marketplaces need to do much more to prevent unsafe products being sold through their platforms. We’ve been calling for marketplace sites to be held to the same standards as traditional retailers, and to ensure the products sold through their platforms meet UK standards. 

We're calling for the government to ensure the Product Regulation and Metrology Bill gives online marketplaces clear legal responsibilities to prevent the sale of unsafe products, and for the regulator to be given enforcement powers, including the ability to impose heavy fines. 

*We conducted a nationally representative survey of 2,065 UK adults in December 2023 that asked shoppers about their use of online marketplaces in the past two years.