How to update outdated browser on OS X Yosemite

I have good news and bad news.

You can upgrade a Mid-2011 iMac as far as macOS 10.13.6 (High Sierra). High Sierra is still extremely outdated and it is very hard to find new application software for it these days, but you will be better off with High Sierra than with Yosemite.

The latest version of Firefox that will run on Yosemite is Firefox 78 ESR.

Mozilla – Firefox Mac OS X 10.9, 10.10 and 10.11 users move to Extended Support Release

It's probably more up-to-date than Yosemite's version of Safari – but it stopped getting critical security updates in October 2021. It has gone nearly three years without any updates of any kind.

The latest version of Firefox that will run on High Sierra is Firefox 115 ESR.

Mozilla – Firefox users on macOS 10.12, 10.13 and 10.14 moving to Extended Support Release

It has been getting critical security updates, but will no longer get them as of some time this month. Still, I think it's a better choice than Yosemite's version of Safari (which might not even be able to access many https sites) or than Firefox 78 ESR.

For reference, the current version of Firefox is 130.0. It requires Catalina or later.

John Galt wrote:

A mid-2011 model Mac can be upgraded to run macOS 10.13 High Sierra. To learn how to do that please read How to download and install macOS - Apple Support. Scroll down to High Sierra 10.13.

I believe that the version of Safari in Yosemite predates the changes made to tighten https security.

It might be necessary for the OP to

• Display the http address of the High Sierra link, and enter that address into Safari on the old Mac, or
• Save that link as a bookmark file that can be transferred to the old Mac via a USB flash drive, or
• Use a modern Mac or PC to download the .DMG file at that link onto a USB flash drive for transfer to the old Mac (thus bypassing the need for the old Mac to make a https connection)

The old Mac will need to be running some version of the OS to make use of the .DMG containing the installer.

It would be a good idea for the OP to make a bootable clone backup of their Yosemite system before attempting the High Sierra upgrade, just in case something goes wrong, and they need a way to recover.

Yosemite's version of Safari won't work for lots of websites, not the least of which is this one (Apple Support Communities). I use Firefox ESR for iMacs that can't be upgraded to HS.

Safari for High Sierra will work. Brave will work even better.

A mid-2011 model Mac can be upgraded to run macOS 10.13 High Sierra. To learn how to do that please read How to download and install macOS - Apple Support. Scroll down to High Sierra 10.13.

Having said that even High Sierra is rather outdated at this point. If you need a newer browser than the Safari version incorporated in High Sierra, consider Brave, or Firefox.

https://brave.com/

https://www.mozilla.org/en-US/firefox/new/

Both of them are outdated as well, but not as outdated. They ought to be able to cope with the latest websites.