i have a iMac (27-inch, Mid 2011) with Yosomite 10.10.5. What is the latest update i can install

Hello!

The latest version of MacOS available for your iMac is High Sierra (10.13.6).

Since you have 10.10.5, you can directly install High Sierra from the App Store.

In this page you can find the proper version: How to download and install macOS - Apple Support

Be sure to select High Sierra in the "App Store" section.

Try downloading and installing High Sierra from the Safe Mode according to How to use safe mode on your Mac.

NOTE 1: Safe Mode boot can take up to 3 - 5 minutes as it's doing the following; 

• Verifies your startup disk and attempts to repair directory issues, if needed

• Loads only required kernel extensions (prevents 3rd party kernel/extensions from loading)

• Prevents Startup Items and Login Items from opening automatically

• Disables user-installed fonts 

• Deletes font caches, kernel cache, and other system cache files

NOTE 2: if you have a wireless keyboard with rechargeable batteries connect it with its charging cable before booting into Safe Mode. This makes it act as a wired keyboard as will insure a successful boot into Safe Mode.

Yup, what Michaelhere posted… he’s correct.. on a side note the max ram you can put in your iMac is 32 GB, if you wanted to, that is…

Oh, and there’s a very important bug you should know about Yosemite ( Mac OS 10.10.5) .., the Wifi doesn’t work AT ALL… so an even better reason to go for High Sierra…

John B

Even High Sierra won't be enough for a lot of newer applications. But if you upgrade to High Sierra, there are a few ways you could extend the life of that iMac.

You can download Firefox (Extended Service Release). It's not on the main branch, but I believe it will still get some security updates until some time in 2024. Safari is tied to the OS, which means that the versions of Safari that you can run in El Capitan (final update: July 2016) and High Sierra (final update: July 2018) are old, and may be having trouble with current Web sites.

You could download LibreOffice 7.4.7 (the last version that runs on High Sierra) from the LibrreOffice archives. You can't get Microsoft Office for El Capitan or High Sierra any more – Microsoft's policy for Office/365 is now that they will support only the last three major versions of macOS.

There are others that might be worth grabbing. But even a lot of Open Source projects that have put out software compatible with older versions of macOS are starting to require versions of macOS more recent than High Sierra for their latest releases.

By George ! I think Old Toad has struck gold on this one… Huzzah for him! huzzah ! It should work… I didn’t know for sure if + that you could download and install High Sierra in Safe Mode, but you can and must be able to… it’s Safe mode after all… although High Sierra has been officially EOL’ed… it may still yet be available, but that’s up to Apple… this is the best info I’ve found, current as of July 20,2023: Can I still get macOS High Sierra?

In general, you can go to App Store to search and download macOS High Sierra installer. However, some people report that they fail to find the macOS High Sierra download in App Store. In this case, you can try clicking the macOS High Sierra link. It will lead you to the App Store macOS High Sierra page.

so if it might still be available… that’s officially where it would be… if it’s gone, well, call Apple support… or ask someone else here- I’m fresh out of ideas, tapped out…

John B

Try downloading and installing Sierra, whose installer is available as a .DMG (disk image) file. Then retry the High Sierra installation, using the Sierra versions of Safari and the App Store. Hopefully will get you all the way to High Sierra, but at least should get you to Sierra.

Look in your Applications and Downloads folders, and see if there is a copy of the installer there. If there is, drag it to the Trash. Then try downloading a new copy from the App Store.