Make image browsing (the film viewer) faster by preloading the following page's image
Currently, if you're looking for an ancestor in an unindexed collection, you might load page 1, look for your ancestor, click "next page", wait a few seconds for page 2 to load, look for your ancestor again, etc.
However, what if you didn't have to wait a few seconds between each page load?
HTML has a few options for preloading assets. See preconnect, prefetch, preload, and prerender on https://developer.mozilla.org/en-US/docs/Web/HTML/Link_types, all of which have varying browser support and different nuances.
With preloading enabled, while I'm looking for my ancestor on page 1, my browser can be downloading the image of page 2 in the background. When I switch to page 2, I immediately see the image because it was already downloaded. In the meantime, page 3 is now being downloaded in the background, etc.
If a user already knows what image they want to see, e.g. an image linked from the Sources tab of a person's profile, then this doubles the image bandwidth both for the user and FamilySearch.
However, if the user doesn't know what image they want to see, e.g. they're browsing N pages in a collection to find their ancestor, the bandwidth required is N+1, i.e., one more page is loaded than is needed.
There are some tradeoffs to consider for sure, but I think this could really speed up image browsing and ancestor finding on unindexed records.