Making backups of your Mac’s Photos Library are among the more popular questions to Mac 911. It’s not enough for many people to have one backup made by Time Machine; a lot of you also want a manually-created backup that’s more accessible in case something goes wrong. The catch to manually backing up a Photos Library is to use a method that isn’t tedious.
The answer may lie with sync software. Sync software lets you keep files and folders in two locations (or more) up to date with each other. Sync software has been around since the earliest days of the Mac, and I’ve used many sync apps.
My current favorite sync app is ChronoSync. It’s kind of a kitchen-sink program: it can do any kind of thing you could plausibly want to do to keep things synchronized, cloned, backed up, archived, whatever. It requires a little study to master, but it’s worth it. It’s $50 but it has a perpetual upgrade license, and all future improvements are included.