Close an Open Safari Tab on Other Devices by Swiping Your Finger Across the Screen
iOS: Apple’s Safari makes it easy to view open Safari tabs from your iPhone or iPad. This means that others can see what is open to you. If you want to close one of these tabs remotely, swipe right.
You need to register your mobile devices and computers with the same Apple ID, but after that everything should sync. Then pull up the tabs on your current device, pull down and you will see your iCloud tabs on other devices. Swipe right and tap Delete to close this tab on your source device.
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