Que estas?

Hola Brooklyn C.

I think you’re referring to ¿Qué tal estás? rather than ¿Qué estás?.

Both ¿Cómo estás? and ¿Qué tal estás? mean “How are you?”. The difference is very small: ¿Cómo estás? is the most common and neutral form, while ¿Qué tal estás? is also correct and often used in Spain, sometimes sounding a bit more informal or friendly.

So yes, you can use either one as a greeting.

Un saludo

Silvia