Something has been happening with Facebook since yesterday. I am using Safari.
The page is slow to load, and often doesn’t load completely. If I click on the ‘bell’ icon, it doesn’t always show me the new notifications. My computer gets warm, and the fan comes on. I have gone to Safari => Preferences => Privacy => Manage Website Data and have deleted everything with ‘face’ in it. I re-logged into Facebook, and my MacBook warms up and the fan comes on.
It sounds like for whatever reason the Facebook page is running your processor at 100%. You may have malware running from Facebook.
Does the Mac have anything to display running processes? Whatever is chewing up your processor may just show up as ‘Safari’, but it may show as a separate process.
Facebook has a habit of doing A/B testing and just throwing features or upgrades out there to a percentage of users to see how they work and get feedback (not necessarily in the form of a survey but more like “how many people who saw this feature used it?” or “How was performance for the people who saw this feature?”)
Whenever anything starts acting weird with Facebook I tend to give it a day or two before trying to fix it on my end. One does have to suffer through it in the meantime, which is annoying. But in every case so far, it has worked itself out.
If it’s working in FF for you you might consider using it in FF for a few days and revisit it next week.