Communicate between app

I create 3 different app using this blynk, can this 3 app communicate each other and how to make it?

Not too sure why you would want that but won’t be easier to create a single App with 3 tabs?

If in a single app you can use Bridge.

Alternatively with 3 different apps I’d communicate thru the hardware side

Do you meen three different projects in the same App & account? If so, then use Bridge.