Now go to their websites, sign up for their services, and test out their core features.
Really try out their service and see if you really offer something different from what they can offer. Most startups fall into the trap of thinking they know what their competitors are doing.
"It is said that if you know your enemies and know yourself, you will not be imperiled in a hundred battles; if you do not know your enemies but do know yourself, you will win one and lose one; if you do not know your enemies nor yourself, you will be imperiled in every single battle." - Sun Tze
The truth is that one of the key reasons why startups fail is that they fail to fully educate themselves on the existing available features, and they spend months finishing their product to realize that they've been building an existing feature.