How to tell if my adapter is original or counterfeit?

Hey there,

See ☞ Identify counterfeit or uncertified Lightning connector accessories - Apple Support

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See ☞ About Apple USB power adapters - Apple Support

Kind of hard to tell without looking for exact details. However, all of mine either came with an Apple device or I bought it from an Apple Authorized Reseller.

Apple has multiple contract manufacturers making both the power adapters and modular plugs. They may have minor differences depending on the actual manufacturer.