iPhone charging plug right side up Article
This is how I determine which side is up on the charging cord when I plug it into my iPhone.
First note that the plug has a flat tongue which plugs into the iPhone. When the plug is right side up, you will note that the tips of the top side of the leading corners of the tongue appear to have been clipped off.
You can detect this by simply using your thumbnail to explore the top side of either of the leading corners of the plug.
If you use your thumbnail in the same way to explore the top side of the corners of the leading edge of the plug when it is upside down, you will find that the corners do not appear to have ben clipped.