Comment by csande17

For what it's worth, the actual search backend seems to be implemented in the separate "GeoData" extension: https://www.mediawiki.org/wiki/Extension:GeoData

That extension exposes a public API that allows setting any search radius up to 10 km ( https://en.wikipedia.org/w/api.php?action=help&modules=query... ), so presumably there's no barrier to making the search radius smaller, but maybe there'd be performance issues if you allowed making it larger.

(NearbyPages just embeds a Vue app into the page that makes a client-side fetch() call to invoke that API with a hard-coded radius.)