Your widget runs, where you say it runs
Your embed code sits in the source of every page it's on, which means it can be copied. Onto a staging site nobody took down. A partner's landing page. A fake version of your store, now carrying your real chat window.
Trusted domains end that. You name the domains allowed to host your widget. Nowhere else loads it.

As broad or as strict as you need
One storefront, three regional ones, a separate help center? Trust the domain and its subdomains in one go. Need production in and staging out? Add exact entries instead.
Add them by hand, or don't
Your widget already tells us which sites it runs on, so you can pick from a detected list instead of typing. That list is built from aggregated traffic, so a widget you installed five minutes ago won't be on it yet. Give it 10 to 30 minutes.
Available now
Settings > Security > Trusted domains. Same feature you know from LiveChat, so there's nothing to relearn if you're moving over.