[ancarda]

Why use a spinner for downloading? Don't you know how many bytes you need to fetch and how many you have received so far?

wget has a progress bar, and it works perfectly fine.

EDIT: Though, if the server does not have a Content-Length header, you will get an indeterminate progress bar (a kind of spinner, I suppose) in web browsers, if that's the kind of thing you mean?

[_jal]

Downloads can occupy some fuzzy middle ground between unknown and deterministic.

The normal case is that bandwidth throughput can be estimated well enough to make humans happy. But a broken network throws that out the window and will do its best to find ways to make your progress bar behave weirdly.

I can't remember what it was, but there was a Mac app a very long time ago (System 7 era, in the 90s) - maybe a news reader? - that would eventually hide the progress bar and show a message about bad networking when that happened.

[masswerk]

There are browser APIs, as well. However, network performance may vary. Personally, I would add textual information, like an estimate of the time required.