URL preview is a safety feature offered by URL shortening services that allows users to see the destination URL before committing to visit it. By appending a special character (like "+" or "~") to a short URL or visiting a dedicated preview page, users can inspect where the link leads without being redirected.
URL preview addresses one of the primary security concerns with short URLs: the inability to determine the destination from the link itself. While a full URL like "https://example.com/products/shoes" clearly indicates the destination, a short URL like "https://tan.be/x7K" reveals nothing about where it leads. Preview functionality bridges this gap by providing transparency. Internet safety books on Amazon discuss safe browsing practices.
URL shortening services implement preview in various ways. Some display a simple page showing the destination URL and basic metadata. More advanced implementations fetch and display the destination page's title, description, and thumbnail image, giving users a rich preview of the content they are about to visit.
For maximum security, preview pages should also display safety indicators such as whether the destination uses HTTPS, whether the domain is on any known blocklists, and when the short URL was created. Web security tools books on Amazon cover safety verification approaches.