Jean Fredette wrote:
For some things like speedtests and video downloads, the web servers stop
working if you don't keep "their tab" in "focus" (I think that's the word
to use).

An example is speedtest.comcast.net which doesn't like when you focus on
something else while it's running. Luckily it doesn't take long but plenty
of other things do.

Is there a way to trick a browser tab into THINKING it's in focus?

Open the tab in a separate browser window.

In case that does not work for you, some browsers have their own options
to let background tabs run like they were still in focus. The details
will depend on which browser you use.