Why double-selling happens
When one item is active on two marketplaces, a buyer on either platform can purchase it. If the other listing stays live too long, a second buyer may buy something you no longer have.
Manual delisting can work for a very small store, but it depends on you seeing the sale notification immediately and acting quickly.
Link listings instead of tracking them in your head
A safer workflow keeps a record that the eBay listing and Depop listing represent the same physical item. That link is what lets a sale on one side trigger action on the other.
Listalong keeps linked listings visible in one dashboard so you can see what is imported, approved, live, sold or needing attention.
Use automation, but keep realistic expectations
Listalong normally removes matching sold listings within minutes. That greatly reduces the risk of a double sale, especially when you are asleep, packing orders or away from your phone.
No cross-listing system can promise that simultaneous purchases will never happen, so sellers should still keep stock counts and marketplace messages under control.