A visitor who never scrolls past the first slide should not pay for the third
Several designs open with a full-width slideshow. It is a good look for an actor, because it lets you lead with an image rather than with text. It is also the single heaviest thing on those pages, and how it loads decides whether that costs you anything.
The setting that matters
Sliders have a lazy-loading mode, and the modes are not what their names suggest. One mode loads every slide up front. Another, which sounds like the careful option, actually loads four: the first, the second, the last, and the one before the last. Only a third mode loads each slide as it reaches it.
Measured on a real customer home page, the middle mode downloaded three hero images before the visitor had seen anything but the first one. Forty-six kilobytes, ninety-six, and thirty-eight. That is 134 KB spent on pictures nobody had looked at yet, roughly a tenth of the whole page, on a carousel that waits five full seconds before advancing.
Your slider loads the slide it is showing. The remaining slides arrive during that five second gap, which is an enormous amount of time for a forty kilobyte image, so nothing about the experience of watching it changes.
Why the first slide is still instant
The obvious worry with lazy loading is that the first thing a visitor sees becomes the slow thing. That would be a bad trade, because the first slide is the one that matters.
It does not happen here, because the first slide is preloaded explicitly by the page itself, separately from the slider. The browser is told to fetch it as a priority before the slider has even initialized. So the visible image is already in cache when the slideshow starts, and the change only affects images that were being fetched speculatively.
Where this sits in the wider picture
Slider weight is one item on a longer list. Serving smaller files at the same visible quality reduces every image on the page rather than just these. Declaring image dimensions stops the layout jumping while they arrive. Video embeds were the other large cost on a typical actor home page.
If page speed is not something you have thought about, the general case is the place to start, and mobile is where it actually gets noticed. Choosing a design that leads with an image at all is a separate decision, and you can look through the catalog before making it.
