For Apple products, we can take following points in consideration to detect if the charger is original or not.
An Apple Lightning to USB cable has “Designed by Apple in California” and either “Assembled in China,” “Assembled in Vietnam,” or “Indústria Brasileira” on the cable about seven inches from the USB connector. You’ll see a 12-digit serial number at the end of this text.
The cable has single piece, smooth rounded, smooth, gold- or silver-colored contacts
The charger’s end that fits inside the phone’s charging hole has gray/metallic faceplate insert.
The charger fits perfectly inside the phone.
The charger cable when connected to a computer, the device should be recognized without any glitch.
The charger cable is stronger and will work even if it is bent many times.
The charger is strong and thus has more life expectancy.
For Samsung and other android phones, following points can be considered:
The first thing you will look for is the Samsung logo printed on your phone charger .It should be printed in raised ink, straight across, with no printing mistakes or ink runs. It will also not be a sticker.
Look at the information printed on the back of the actual phone charger. Once again, it should be clearly printed in raised ink, and not crooked or runny. It should not be a sticker.
Your charger should have no visible seams or material defects. This means it should not look easy to open, and you should not see bits of plastic sticking out on corners or edges.
The charging dock is a single piece without separate parts joined together. The dock is a smooth single material piece.
When properly connected, the large USB end will smoothly slide into the charger. It should be easy to push in, and fit snugly, without wobbling or being loose. In the event it is loose, either the cable or the charging port has been damaged, or it is fake.
Finally, plug your Samsung phone into your computer. If the phone is recognized, then you have an original cable. However, if it is not recognized, you may have a fake cable or phone.