When do we elide “dove è” into “dov'è”?

Question

I have gone through various web pages about elision in Italian. All of them mentioned that we usually elide words like *di, la, le, nella, questo*, et cetera. But none of them mentioned the elision of *gli* and *dove*.I searched for more and learned that words like *gl'insulti* are old usages and we don't usually elide *gli* nowadays. But what about *dove*? I see *where is* translated into **dov'è** but no one told me elision goes like that. When (in what cases) is *dove è* elided into *dov'è*?

Answer 1

The elision of dove before è is optional, so there are no rules telling us where to use dov'è or dove è.