Infinite scroll

Infinite scroll takes the reader’s scroll as the request. A sentinel sits at the end of the list, and when it comes near the viewport the next page is fetched and appended, so the gesture that was already happening does the paging. The mechanism on the web is usually an IntersectionObserver watching that sentinel, which is why the pattern is also written as a threshold: load when the reader is within a screen or so of the bottom, early enough that the new items are in place before the old ones run out.

Its family resemblance is to load more, and the difference is one of consent. Load more ends the list with a control and waits to be asked, which gives the reader a stopping point, a stable footer, and a moment to decide they have seen enough. Infinite scroll removes the asking. That suits a feed with no destination, where the reader is browsing rather than looking for one thing, and it suits touch, where a flick is cheaper than a tap on a small target. It suits a results list badly: someone comparing options wants to know how many there are, to keep a place, and to come back to it, and pagination is the pattern that gives them a numbered place to come back to.

The costs are well documented and mostly structural. Anything below the feed becomes unreachable, because the bottom moves away as fast as the reader approaches it, so a footer with the settings, the terms, or the contact link has to move somewhere else. Position is lost on navigation unless the pattern is built to restore it, so tapping an item and coming back can mean scrolling the whole way down again. The document grows without limit, which costs memory and eventually smoothness, so long feeds need windowing that recycles rows rather than keeping every one of them. And there is no sense of scale: a reader cannot tell whether they are near the end of the results or at the start of a river. Keyboard and screen reader users feel each of these more sharply, since content that arrives without an announcement is content they were not told about.

The mitigations are the pattern’s real craft. Keep a visible loading row so waiting looks like waiting rather than like the end. Announce arrivals politely, so the count that changed is heard as well as seen. Restore the scroll position and the loaded pages when the reader comes back. Cap it: many feeds load three or four pages this way and then plant a button, which keeps the effortless part and gives the reader back the choice. And keep a paged route to the same content underneath, because a search engine, a shared link, and anyone who wants page nine all need an address that a scroll offset cannot give them.