Your and You're

Day 1,931, 02:19 Published in Australia Australia by Jakesweet27
This is my grammar lesson so you don't get trolled on the internet. (P.S. don't make fun of my horrible English either.)
(P.P.S I may be the grammar Nazi)

You're is short for you are.
Your shows that something belongs to you or is related to you (e.g., your car, your father).

You're
You're is a contraction of you are. It has no other uses. This is a 100% rule. If you cannot expand it to you are in your sentence, then it is wrong.

Examples:

The trouble with the rat race is that even if you win, you're still a rat. (Lily Tomlin)
(Expands to you are - correct)

Doing nothing is very hard to do. You never know when you're finished. (Leslie Nielsen)
(Expands to you are - correct)

Please ask Joan to post the parcel when you're in London.
(Expands to you are - correct)

You said that you couldn't believe you're ears.
(Does not expand to you are - should be your)

Your
The word your sits before another word (usually a noun or a pronoun) to show that it belongs to "you" (e.g., your car, your arm), is of "you" (e.g., your picture, your photograph) or is related to "you" (e.g., your uncle). Your is a possessive adjective. (Other possessive adjectives are: my, your, his, her, its, our and their.)

Have a good day. #WarCrew