The Unix underpinnings, frameworks, and platform security model behind Apple's desktop OS.
Distinguishing normal, temporary Spotlight indexing load from a genuinely stuck reindex loop, and resolving the latter instead of tolerating it.
Why the login keychain stops matching your account password after a reset, and how to fix it without losing every saved password inside it.
Reading the memory pressure gauge correctly, telling normal swap usage from a real problem, and identifying which process is actually responsible.
A Time Machine backup taking hours, or stuck at 'Preparing Backup,' usually has an identifiable cause - the first backup, local snapshots, or something else.
About This Mac says the disk is nearly full, but visible file sizes don't come close - how to find what's actually consuming space, hidden data included.
Force Quit doesn't work, the icon keeps bouncing, or it's stuck 'Not Responding' indefinitely - the actual escalation path, gentlest to most forceful.
Working through the network preference files macOS updates most commonly leave inconsistent, before assuming a hardware or router problem.
Creating, listing, mounting, and cleaning up APFS local snapshots directly - the same mechanism Time Machine uses, available for manual, ad-hoc use.
Checking whether an app's code signature and notarization are actually valid from the command line, not just Gatekeeper's pass/fail dialog.
Understanding the container/volume distinction that makes APFS different from older partition schemes, and using diskutil to manage volumes directly.