Hi Ajogamer, if you hover your mouse over the tab to view the full title, is the number in there and just not visible because the tab is too narrow, or is the number completely missing? If the number is missing and you switch over to that tab, does it update at that time?

Thanks for the response. As for those questions: The number's completely missing even if I hover over the tab. If I switch into a tab that would normally display notifications, the number still won't be there despite there often being indication of new messages on the webpage itself (which would normally trigger the numbered notification on the tab).

It isn't an issue of the tab being too narrow either, since I normally have only a few tabs open, and there's still plenty of blank space on the tab to have room to display the number as a result.

I wonder if some "background tab" actions are being deferred or ignored. Have you changed any settings related to notifications or "service workers"?

You can submit this to the developers by filing a bug, but first, I think it's a good idea to try:

New Profile Test

This takes about 3 minutes, plus the time to test your sites, which might take a while depending on the frequency of updates.

Inside Firefox, type or paste about:profiles in the address bar and press Enter/Return to load it.

Click the Create a New Profile button, then click Next. Assign a name like Oct2017, ignore the option to relocate the profile folder, and click the Finish button.

After creating the profile, scroll down to it and click the Set as default profile button below that profile, then scroll back up and click the Restart normally button. (There are some other buttons, but please ignore them.)

Firefox should exit and then start up using the new profile, which will just look brand new.

Do your sites in background tabs update the count in the new profile?

When you are done with the experiment, open the about:profiles page again, click the Set as default profile button for your normal profile, then click the Restart normally button to get back to it.

I tried the New Profile Test you suggested, which unfortunately didn't seem to help. It still had the same issue with notifications not being indicated on the tab as new tweets arrive.

I don't believe I've changed any settings related to notifications. My original suspicion was that some sort of setting changed on its own, but I couldn't find any setting relating to notifications on tabs when I searched Firefox's settings. I don't believe I changed any settings related to "service workers", since I've never heard of service workers before, and am unsure what they are. Are there some settings related to that I should check?

Is there anything else you'd suggest I take a look at or try?

"Service workers" are a feature sites can use to more efficiently keep a tab connected to the site for updates instead of using a script to check every so often. Disabling push notifications is an example of a settings change that could block service workers.

I don't use Twitter, but maybe I can test this out if I subscribe to some active posters?

I see, thanks for the explanation. I'm unsure if this has to do with service workers or not, but perhaps I should also clarify that the contents of the tab are still updating when I have it as a background tab, it's only the notification on the tab itself that is no longer displaying.

For example, the webpage itself shows the on-site notification that normally displays just above already viewed tweets (such as "5 new Tweets") but I no longer see the any numbered indication (such as "(5)") on the tab itself.

If you wanted to test this out with Twitter on your end, think you wouldn't even need to register an account, since I noticed both the on-website and on-tab notifications displaying for me when not logged into Twitter in the past , if I left a tab open on the page of a user that tweets a lot.

I do get the (1) in the tab when there is "See 1 new tweet" in the page. I'm sure our configurations are a bit different, but I don't yet have a sense of what that difference is.

The way it works is that a script in the page updates the title of the document, which prompts Firefox to update the tab. Could you check whether the title is getting updated? Here's how:

While the page is indicating new tweets, open Firefox's Web Console in the lower part of the tab using either:

• Ctrl+Shift+k
• "3-bar" menu button > Developer > Web Console
• (menu bar) Web Developer > Web Console

In the line at the bottom, paste this little bit of script and press Enter to execute it:

document.title;

I am attaching a screenshot illustrating the result in my case. Does yours show the number, or no number?

It looks like it shows no number on my end after following those steps, even though the page is indicating a new tweet. I attached a screenshot of what I see on my end.

I'm unsure why it is, but today the issue seems to have fixed itself on the few affected sites I frequent, so I guess this issue could be considered solved now. I didn't change any settings or even restart the browser, (in fact, don't think I even refreshed the page on some of the affected tabs), so I really don't know what fixed it, but I'm certainly happy to have those notifications displaying again.

Nonetheless, I definitely appreciate all your assistance in trying to narrow down and figure out the cause.