A large proportion of what is sold on major online marketplaces is sold by third parties rather than by the platform. The distinction is disclosed in small text and determines a great deal.
The three arrangements
Worth distinguishing since they behave differently.
Sold and shipped by the platform, where the platform is the retailer and is responsible for the product, the delivery and the return.
Sold by a third party, fulfilled by the platform, where the seller is the retailer and the platform handles storage and shipping. Returns generally go through the platform's process, and the seller is the counterparty.
Sold and shipped by a third party, where the platform is only the venue. Delivery, returns and support are the seller's, and the platform's involvement is limited to the transaction.
The middle case is the one that causes most confusion, since fast platform delivery implies the platform is the seller when it is not.
Why it matters
Several practical consequences.
Return policies differ. Platform-sold items generally carry the platform's policy; third-party items carry the seller's, subject to platform minimums.
Warranty and support route to the seller, which for an overseas seller can be impractical.
Recourse differs. Platforms operate guarantee programmes covering third-party purchases, with conditions and claim windows.
And responsibility for product safety and compliance sits with the seller, which for goods shipped directly from abroad has been the subject of substantial regulatory attention.
The commingling issue
A specific practice worth understanding.
Where multiple sellers offer the same item and the platform holds stock in shared inventory, units may be pooled by product code rather than tracked by seller.
Which means an order placed with one seller can be fulfilled from stock supplied by another.
The concern, raised repeatedly, is that a counterfeit entering the pool can be shipped to a customer who ordered from a legitimate seller.
Sellers can generally opt out of commingling, and platforms have introduced measures to address it, and the structure means buying from a reputable seller does not fully guarantee the specific unit's provenance.
Counterfeits
The area where the marketplace model has attracted most criticism.
Categories most affected have historically included consumer electronics accessories, cosmetics, supplements and branded goods generally.
Platforms have invested substantially in detection and brand protection programmes, and enforcement actions and lawsuits have followed.
The practical defences remain the same. Buy from the brand's own storefront or an authorised seller where identifiable, check the seller name against the brand, and be suspicious of prices substantially below the market.
For anything where a counterfeit would be dangerous rather than merely disappointing — anything ingested, anything electrical, anything protective — the argument for buying from an authorised source directly is considerably stronger.
Seller assessment
What to look at, since the information is available.
Feedback volume and rating over a long period rather than recent only.
How long the seller has been trading, which is generally shown.
The business information, which platforms in several jurisdictions are now required to display, including a registered address.
And whether the same seller offers a coherent range or an unrelated assortment, which is a reasonable signal about what kind of operation it is.
The returns route
Where the difference is most immediately felt.
Platform-fulfilled returns are generally straightforward regardless of seller.
Seller-fulfilled returns may require shipping to a distant address at your cost, which for a low-value item exceeds the refund.
Checking the return arrangement before purchasing is a few seconds and is the difference between a return being practical and being theoretical.
What I check now
Who the seller is, on every listing above a trivial amount.
Where returns go and who pays.
Whether the seller is the brand or an authorised distributor for anything where authenticity matters.
And for anything safety-relevant, buying from the brand directly or from a conventional retailer, which costs marginally more and removes the question entirely.
Price differences between sellers
Worth understanding since the same listing can carry several.
Multiple sellers offering the same item compete on price, and the default seller shown is determined by an algorithm weighting price, delivery and seller performance.
Other offers are visible behind a link that most buyers never click, and they are frequently cheaper.
The trade is generally slower delivery or a less established seller, which is a reasonable choice to make deliberately.
Checking the other offers takes one click and is the most consistently overlooked saving on marketplace platforms.
Product safety and imports
An area of active regulatory attention.
Goods shipped directly to consumers from overseas sellers may not meet destination safety standards, and enforcement against distant sellers is difficult.
Regulators and consumer organisations have repeatedly tested marketplace goods and found products failing safety requirements, particularly electrical items, chargers, and children's products.
Several jurisdictions have introduced or proposed obligations on platforms to take responsibility for the safety of goods sold through them.
Until that settles, buying safety-critical items from conventional retailers or authorised sellers is the practical response.