in kentico 13 when i am debuging any widget its calling two times

I don't think it should be calling it twice - does this happen to ALL widgets?

Is it the same widget actually being rendered twice? E.g. do you have a resource being requested on page load that is 404'ing and potentially loading a widget on the 404 page?

yes its happening to ALL widgets. no in browser it display only one widget but calling it twice

I've tried to replicate this on a few websites we've built and this never happens.

Without access to the code to see what you're doing I think this will be hard for anyone to diagnose via DevNet.