You should pay attention to the conversations that you are having with this person and you will be able to easily tell when they contradict themselves.
A catfisher is normally a person who creates a false online persona in order to lure an unsuspecting person into a false romance.
Being that the person that you are interacting with on the online dating site is most likely someone that you don’t know, you couldn’t possibly determine who you are dealing with through purely text-based interactions.
The problem with solely relying on this form of communication is that you could easily be misled by someone.