What is this USB-C 20W Power Adapter?

If it’s a good counterfeit that is no way to tell. I would need to hold it in my hands and study it carefully to make any determination. But if that is a sticker on it I would be very suspicious; Apple never puts stickers on its products.

But if you buy one from Apple or an Apple authorized reseller it will be genuine, so if you have any doubt just do that.

No one here would know, we're just all users like you. Try contacting Apple -

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https://getsupport.apple.com/

Is this original??