What happens when you open a photo
When you ask to see a photo or a video, we check right then that you are allowed it, and only then is it shown to you. Nothing is left behind that somebody else could pick up and follow.
Every link expires, quickly
A link to a photo or a video stops working soon after it is made. Sent to somebody else, it has almost certainly stopped working before they open it, and it cannot be kept in a bookmark for later.
A file has no address of its own
A file here has no lasting web address that anybody could copy, share, index or guess. It is only ever reached by the person allowed to see it, at the moment they ask.
A copy carries the account it was shown to
What you are shown is marked with the account it was shown to. The mark does not stop anybody copying anything, and it is not meant to. It means that if a file turns up somewhere it should not be, it can be traced back to the one account it was handed to.
Being allowed is checked every single time
Whether you may see something is checked every time you ask, not once at the start. So when access ends it ends at once, and nobody keeps access by holding on to something they were given earlier.
If something of yours turns up elsewhere
Tell us, and give us where you saw it. Because a copy carries the account it was shown to, we can often say which account was handed that exact file, and act on that account. What we cannot do is take the copy down from somewhere we do not control. That part is between you and whoever is hosting it, and in many countries the law is on your side there.
Nothing here stops a camera
Anybody can point a phone at a screen and photograph what is on it. No website can stop that, and neither can we, so we are not going to tell you that copying is impossible here. What is true is that copying is harder here than it is in most places, and that a copy points at one account. Please post on that basis: assume a copy of anything you put anywhere exists somewhere you cannot reach.