I followed Prop Swinger’s Instructions (many thanks - we are making progress) on the iMac using the YouTube “Please update your Browser” page. The stuff that opens at the bottom is different but I eventually found my way to User-Agent. It shows:
User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.10; rv:50.0) Gecko/20100101 Firefox/50.0
I then did the same on the MacBook Air, which although it has the older OSX 10.9.5 has never displayed this problem. Since it never receives the “Update your browser” page I used the YouTube page for cookies. User-Agent for this page shows:
User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_11_5) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/51.0.2704.106 Safari/537.36 OPR/38.0.2220.41
Any thoughts on why the two User-Agent sections are different, apart from the OSX version? Both Macs were updated to Firefox 78.11.0esr on June 1 2021. Interesting that the correct version of OSX is not shown in User-Agent on either Mac.
We are using Firefox 78.11.0esr on both Intel IMacs with OSX 10.9.5 on the MB Air with no issues and OSX 10.11.6 on the iMac which receives the “Update your browser” pages. It seems no change is needed on the MB Air but something needs to be changed on the iMac. How may I correct this on the iMac?
Thanks to various for info on Mac OSX versions. The iMac cannot be upgraded beyond its current 10.11.6 as Apple ceased providing updates for it. It does all that we want and is especially useful as it has a built in DVD player for our considerable collection. The MB Air’s OSX version will be upgraded after a couple of security issues have been addressed.