Filmstrip

A filmstrip is a rail of small stand-ins that drives a big view. The rail holds the whole set at once, or as much of it as will fit before scrolling, and the large pane holds exactly one item. Picking in the rail changes the pane; the rail itself never moves on to anything. That split is the point: the reader keeps an overview of where they are in a set while looking closely at one part of it.

The nearest neighbour is the carousel, and the two are often confused because both hold a set and show one thing. A carousel moves a viewport over the set, so the set is only ever partly knowable and the reader navigates by stepping. A filmstrip shows the set and the item at the same time, in two regions, so nothing has to be remembered between steps. If your rail has no big pane beside it, you have a scrolling gallery; if your big pane has no rail, you have a carousel with better manners.

The parts have their own words. Each small image is a thumbnail, and it earns its place only if it is croppable to a consistent box: a rail of ragged shapes is unscannable. A lightbox is the other way to show the big version, over the page rather than beside the rail, which suits a grid of images better than a working review does. Slide sorters, page navigators, video scrubbing rails, and photo pickers are all the same component with different content, which is why the word travels well.

Mark the current item in the rail and keep it in view. The commonest bug in the pattern is a rail that scrolls independently until the selected thumbnail is off screen, so the reader loses their place in the set they were keeping an eye on. Give each thumbnail a real accessible name, mark the current one with aria-current, and make sure arrow keys move through the rail, since a strip of images is exactly the kind of control people expect to walk with the keyboard.