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How is the Firefox web browser incompatible with the internet service provider Xfinity ?

I have been using Firefox to download my Xfinity statements for years, including an older version running on Win7. Now, using the latest version of Firefox on a Win10 computer, I can log in to Xfinity, but the Billing "button" doesn't work. This is a third-party service and is not xfinity.com.

It "hangs" for a long time, then shows "Can't find My Account".

However, using Xfinity Assistant to find my bill works (!) -- different code for this feature?

As a further experiment, I tried using Edge. It worked, including Billing. Opening the third-party service isn't fast, but it eventually connects and I can download my bill.

I like running ad blockers, so both Firefox and Edge were running Malwarebytes BrowserGuard and UBlock Origin. In the past, some of Xfinity's code was interpreted as ads and I had to turn ad blocking off, but this time Edge worked and Firefox didn't with ad blocking set identically. BrowserGuard uses a common database for all supported browsers on a given computer, too.

If Xfinity stated they aren't supporting Firefox, it is unlikely they will change their website. Xfinity is a fairly major provider of TV/Internet services. Can't Mozilla investigate this and make Firefox compatible?

Can't Mozilla investigate this and make Firefox compatible?

I does not make sense to make specific versions of Firefox compatible with specific websites as that would break things in a variety of ways over time.

Some sites may just be lazy in only making their sites barely work in the Chrome/Chromium based browsers while if they made the sites to standards then it should work in all modern web browsers.

I figured it out. I made a mistake, first of all. Xfinity is not using a third party -- just misread the URL. However, they are using cookies for communicating between various subdomains on xfinity and Firefox's Enhanced Tracking Protection "breaks" this.

The information in that section of Firefox Settings does state that, if a site is not functioning, the user should try disabling Enhanced Tracking Protection. None of our other sites require doing this, so I was not familiar with this problem. Xfinity gets the honor of being the first, for me.

Some time ago, Xfinity used to require a second login when the user selected Billing. I am guessing they have had trouble passing user account information. The recently fixed this, but whatever code they wrote wasn't compatible with Firefox's default settings.

I think it is interesting that Xfinity's AI Assistant can manage to look up the customer's bill and statement with Enhanced Tracking Protection "On". It doesn't use the "links" on the page, apparently. But the workaround for Xfinity, if you want to use Billing links such as in the Account drop-down menu or Billing on the main page, is to simply turn off Enhanced Tracking Protection.

Adblockers like UBlock Origin and BrownerGuard do not cause trouble.