Among the most useful are Archive Utility, now including Apple Archive compression, and Storage Management. But Network Utility is now non-functional.
CoreServices
If you want to check out your Mac’s Wi-Fi connection, Wireless Diagnostics is ideal. It’ll show you signal dropouts and give its opinion.
What do you do when you open a document, only to find that the wrong app opens it? Here’s how to tackle that and more.
Digging into macOS Sierra and its logs to examine how Recent Items works. Useful insights into Launch Services, and potential historical info about documents opened.
It’s a System Prefs problem. No, a preferences file problem. No, it’s something else, but Apple once again won’t tell us how Recent Items works, or doesn’t.
The Eclectic Light Company 