This extension has served me well. I thank its creator.

does the job!

Even though as delivered Firefox 56 (Nightly) does not display a Window Title (can be added through the Firefox Customize screen), it is still present and other programs can "see" it, whether it is displayed or not, and some programs, including the password manager KeePass, look at that title for matching the screen to the appropriate logon credentials. By having the host name in the Windows title, I can use the host name in KeePass as the unique identifier so, in many cases, logon just becomes hitting a hotkey. (Without this extension, I have to do a search on the KeePass database for the server before I can use a hotkey to paste in the credentials.)

This particular extension is in WebExtensions, so it should survive the Firefox 57 transition.

I have been using extensions like this one for years with KeePass and I have never had any issues with them, but I am thankful that there is an extension, this one, that is already written to use WebExtensions and thereby survive into Firefox 57!

If all you need is a host name in the Windows title for the tab that is in focus, this is GREAT! :)