How to check if my iPhone is original

What is your definition of “original”? All iPhones originally were sold by Apple, Inc., so that isn’t quite what you mean with your question.

You can check the status of your iPhone by entering its serial number here: Apple - Support - Check Your Service and Support Coverage

Check the Apple Warranty Status of the iPhone by entering its serial number on Apple's official website. This allows you to review the device's warranty coverage, eligibility for AppleCare+ or other extended coverage, and support status.

Apple Check Coverage

However, please note that checking the warranty status does not guarantee that the iPhone is genuine or free from counterfeiting. A counterfeit device may use a genuine serial number copied from an original Apple product. In such cases, the serial number may appear valid on Apple's website even though the device itself is not genuine.

Nevertheless, verifying the serial number through Apple's official website is an important preliminary step. It helps establish that the serial number is recognised by Apple, although it does not conclusively establish the authenticity of the iPhone.

For a more reliable verification, cross-check the serial number and IMEI displayed under Settings > General > About with those printed on the original packaging, where applicable. Also, verify that the device is running genuine iOS and that its hardware and features correspond to the claimed iPhone model.

In short, a valid serial number is a useful first check, but it is not definitive proof that the iPhone is genuine.

Are you really asking whether you bought an iPhone, or a counterfeit?

If it was a fake it would probably be running Android