See the web pages open on your other devices in Safari on Mac
The “Show tab overview” button 
lets you view the web pages you have open on your other Mac computers (macOS Sierra or later) and iOS devices (iOS 11 or later). Make sure Safari is turned on in iCloud preferences (on your Mac) and in Settings > iCloud (on your iOS devices).
View a web page open on another device
In the Safari app
on your Mac, click the “Show tab overview” button .You can see the web pages open on your Mac along with lists of the web pages open on your other devices.
Click a web page to open it.
Tip: You can also enter part of the page’s name in the Smart Search field, then click the page in the iCloud Tabs section of your search results.
Close a web page open on another device
In the Safari app
on your Mac, click the “Show tab overview” button .Move the pointer over a web page listed below your device, then click the Close button
that appears to the right.
Hand off a web page between devices
When your iOS device is near your Mac, click or swipe the Handoff icon at the end of the Dock (on your Mac) or on the Lock screen (on your iOS device). The web page you’re viewing on one device is handed off to the other. See Pick up where you left off with Handoff.
You can’t use Handoff to pass Private Browsing windows.