Updating the macOS on 2017 MacBook Air from 10.11 to 10.14

[krs]

I'm finally forced to update a 2017 MacBook Air in the family currently running on ElCapitan with no problems.

Amazon prime will no longer work because (it says) the Firefox browser is out of date, it's at version 78.15 (ESR)
When I check in Firefox, it says the browser is up-to-date and I assume this is the latest version of Firefox that is compatible with macOS 10.11
OK....

So to update that Mac to Mojave, I was planning to do the following:
1. Clone the existing macOS 10.11 and all data completely to an external drive using SuperDuper
2. Erase the internal drive on the 2017 MacBook Air
3. Install macOS 10.14.6 using a USB installer I made a while back (bypassing the expiry date if needed0
4. On start up with macOS 10.14, run Migration Assistant
5. Update Firefox to the latest version

Does that sound OK or is there a better way?
Like after doing the clone backup, can I just install macOS 10.14.6 onto the existing macOS on the 2017 MaBook Air and would that replace 10.11 with 10.14 automatically?

PS: I should really know all that.....

 

[ferrarr]

can I just install macOS 10.14.6 onto the existing macOS on the 2017 MaBook Air and would that replace 10.11 with 10.14 automatically?

Yes, you can do the install "in place" and it will upgrade the OS to Mojave.

That's how I usually do my upgrades. I test them for a couple of weeks or a month then do a clean install.

 

[vansmith]

Amazon prime will no longer work because (it says) the Firefox browser is out of date, it's at version 78.15 (ESR)
When I check in Firefox, it says the browser is up-to-date and I assume this is the latest version of Firefox that is compatible with macOS 10.11

Herein lies the problem - you're using what is called an "Extended Support Release" version of Firefox (see more here). These are releases designed for those who don't want to deal with the quick six week release cycle of regular releases (think corporate environments). These don't update to new versions that aren't ESR ones so you get very long gaps where you aren't running the non-ESR releases (ie. the "regular" ones).

That said, you are right in noting that macOS 10.11 is only supported by the ESR release (see here). Chrome, on the other hand, supports 10.11 (for now). I say all this because it seems like the only reason you're upgrading is because FF doesn't support Amazon Prime video and a solution here doesn't have to involve such a big upgrade. However, if you're all primed (excuse the pun) to go with a full system upgrade, that's probably going to benefit you long term anyway.