When it comes to a huge file (such as huge PDF or upload file to Cloud service) loading or download in a tab, a tiny progress indicator on favicon could be an interesting but also considerate UX experience.
This idea comes from a long time ago and has been realized by so many open-source developers, and it comes to me again when I try to solve this good first issue for the `Send` project from Mozilla https://github.com/mozilla/send/issues/803
Here is React-LoadCon for React community, welcome to play around and feel free to submit your feedback whenever encounters any issue.
https://foreseaz.github.io/react-loadcon/