Where dealing with static file servers:
For URLs that are supposed to include a trailing slash and the server will find that directory and serve its index.html: it’s customary, though not ubiquitous, to redirect from no-slash to slash. (Some, including popular commercial services, serve the index.html file instead of redirecting to add the slash. This is extremely wrong because it changes the meaning of relative URLs.)
But the other way round is not common.
My URLs don’t include a file extension, and I think that’s influencing your perception into thinking no-query-strings is logically a directory name. But it’s not, it’s logically a file name, just with the .html removed as unnecessary.
Take https://susam.net/no-query-strings.html as an example; Susam is more clearly just serving from a file system than I am, and leaves the “.html” file extension in the URL. Do you expect https://susam.net/no-query-strings.html/ to work? I hope not. It’s a 404, just as I’d expect, because there is no directory with that name.
> not-a-404 page
No, that’s a 404, just a plain old boring 404, same as any other. In fact, it’s the same 404 page I’ve been using since 2019, just with dark mode support added.
> extra slashes
Ah, now for that I had to go out of my way, because Caddy misbehaves out of the box: https://chrismorgan.info/Caddyfile#:~:text=%40has%5Fmultiple...
> digression: I love trying "domain.com//" on various sites.
Closely related is adding the trailing dot of a fully-qualified domain name: https://example.com./. I didn’t remember to try this on my new site, but it turns out Caddy won’t talk at https://chrismorgan.info./, so that’s probably good.