This feature is available in Contao 4.13 and later.
If you are in the front end preview, you can create a preview link.
Target URL: The front end URL to be shared.
If you want to change the front end URL you have to create a new preview link.
Expires after: Here you can specify how long the preview link should be available. You can choose between 1 day, 7 days or 30 days.
Show unpublished: Here you can choose if unpublished pages and elements should be displayed when this preview link is shared.
Created at: Date and time when the preview link was created.
Valid until: Preview the date until which the link is available.
Enable: Here you can share the link.