2015 macbook update

Update or upgrade?

2015 Mac OS Yosemite and El Capitan shipped with the Mac at different times through the year. Upgrades for 2015 go all the way up to Monterey via the App Store. Always backup your data and check for compatibility of all apps and device drivers before upgrading.

https://discussions.apple.com/docs/DOC-250004301

Updates on the other hand just improve security to the latest release of a specific annual upgrade.

KSkingdom wrote:

2015 macbook

i have an apple macbook that hasn't had a software update probably since I purchased it in 2015. How do i update it? I would like to sync my iTunes library to my phone and its telling me i need to update it..

You do not say what you are currently running(?) see >About This Mac

You will need to get to at least High Sierra 10.13.6 where the the new Apple File System (APFS) was intoduced before proceeding further...

verify you are using the Safari browser to download/initiate the macOS links.

The older macOS installer backups on this server:

https://support.apple.com/en-us/HT211683

Apple provides non-destructive methods for start-up disk drives for APFS conversion, and hence no data (files or folders) will be lost.

On the other hand, APFS formatting will erase all the files and folders stored on a external hard drive. If not backed up earlier, APFS formatting on the external drive will cause data loss. Even with the start-up drive, one may delete or lose files from the APFS formatted media.

How to Upgrade to APFS if Not Done in macOS High Sierra Installer - The Mac Observer

https://www.macobserver.com/tips/how-to/upgrade-mac-apfs-after-high-sierra/

Non-Destructive APFS Conversion

Restart the Mac into Recovery Mode.

Recovery: https://support.apple.com/en-us/HT204904

Launch Disk utility.

Click-select your named boot volume—the default name is "Macintosh HD" —(Not the physical drive above it.)

In the Disk Utility> Edit menu> select “Convert to APFS"