A yellow heart on Snapchat signifies that you and the other person are each other's number one best friend. This means that the two of you are the ones who send the most snaps to each other compared to anyone else.
In Snapchat, a yellow heart () by the name of a person indicates that you and your friend are each other’s Best Friend (Number 1) Each of you sends Snaps only to each other, and the other person sends you Snaps as well. It indicates good, two-way communication on the app.
The yellow heart on Snapchat means you and that person are #1 best friends. You send the most snaps to each other. It appears when you’re each other’s top contact consistently.