In iOS 13 Safari when clicking on a link that opens a new tab, the back button on the new tab takes you back to the original tab and automatically closes the new tab
Hope the title is clear enough. I haven’t seen this mentioned anywhere.
If you’re on the beta just try clicking on a link that opens an external link on a new tab.
The back button is now enabled and takes you back to the page you came from, while closing that recently created tab.
Love this feature! No more throwaway tabs left lingering forever.