How to Safeguard photos and videos
Check library settings
In Photos, first go to Photos > Preferences > General. If “Copy items to the Photos library” is checked, skip to step 3. If it isn’t, you might have images in Photos linked to external files elsewhere on your Mac.
Consolidate library
To consolidate the photos in the library file, select Photos in the sidebar, choose Edit > Select All, and then use File > Consolidate. This will ensure that everything you see in your Photos feed is now stored in the Photos library.
Export favorites
For particular favorite shots, make copies. Export them to a subfolder within your Pictures folder, upload them to a private Flickr account, or both. The method is less important than it being routine — make it something you just do.
Back up your Mac
When you get your Photos library as you want it, with local copies outside it of your most important pictures, back up your Mac. You now have at least two copies of everything. The chances of you ever losing a photo again are falling.
iCloud Photo Library
To further safeguard photos and videos, enable iCloud Photo Library. Now, anything you shoot on your iPhone is sent to Apple’s servers and then to your Mac (if “Download Originals to this Mac” is checked in Photos’ iCloud preferences).
Back up Photos library
Photos Library (in your Pictures folder) looks like a single file, but is really a package containing all of your photos and videos. Consider periodically copying it to an external drive. It may already be included in your offline backups.