Can I tell if my iPhone charger is original using the Serial number?

Counterfeit products can and often do copy legitimate serial numbers.

Serial numbers are not effective for detecting counterfeits.

A legitimate serial number can be associated with one legitimate product, and zero or more counterfeits.

As stated in the reply above, buying only from an authorized reseller usually gets you a real product.

Grey market can get you counterfeit.

I’d assume all online sales (from non-authorized vendors) are counterfeit until proven otherwise.

What about it? Are you asking if this iPhone power adapter is an original Apple device? If so, providing a serial number will not help. Basically, if you purchased it directly from Apple or an Apple Authorized Reseller, it should be an original product; otherwise, it could be a fake.