It depends on the situation.

First check the credit of the seller, preferably a big seller. Don’t be greedy and buy low-priced products from newly registered sellers, because they are very likely to be fake.

Then look at the credit ratings of those big sellers, mainly the negative reviews. Look at what others have left. Generally, if no one says it is a fake, there is no problem and you can buy it with confidence. Besides, eBay’s policy is to protect buyers. If the buyer receives the product and it is a fake, he can provide proof to initiate a dispute. If the seller cannot provide proof, you will generally be judged as the winner.