Suppose I created a website that cataloged every possible sequence of letters in order.
You would start with the letter "a", could swipe right to read "b", and further to find "aa", or "ab" (appearing in dictionary order, as you would observe on the rows of an excel sheet).
My website has a feature where you can instantly read any text given a numerical ID. The IDs could, for example, be ordered as follows:
Where individual texts in the catalog are separated by red bars, and the blue numbers are their respective IDs.
This website happens to be a harbor for internet piracy. One user, for instance, discovered the numerical ID referring to the entire text of Harry Potter and the Sorcerer's Stone, and has distributed the ID to their friends so that they may read the novel at their leisure.
It's unclear to me where the copyright infringement occurs. Is it the website for "storing" every possible non-public domain text? Is it the user for finding and sharing a number that has apparent meaning to this website?