When a link is shared via iMessage , iOS generates a visual "preview" of that link. Users frequently encountered issues where these preview images appeared small or incorrectly cropped if they did not match recommended social sharing sizes (typically 1200x630 or 1200x683). How to Share Links/Photos on iPhone (2021 Context)

Select to generate a web URL for sharing. Paste that link into a message or email. Share content in Messages on iPhone - Apple Support

In 2021, a common "piece" of sharing was the iCloud Link , which allowed users to send high-resolution photos or videos via a single URL instead of individual files.

If you are trying to replicate or find this "sharing piece," the standard method in iOS 14/15 (the 2021 versions) was: or Safari. Tap the Share button (the square with an up arrow).