“No Space Left on Device” on a Mac: Where the Space Went
No space left on device is an honest error from the kernel: a write was refused because the filesystem had nowhere to put it. The disk is full. What makes it confusing on a Mac…
AirDrop Not Working on a Mac: Check the Interface It Runs On
AirDrop fails in a way that gives you nothing to work with: the other device simply is not there. No error, no explanation, just an empty sharing sheet. The reason it is so opaque is…
Mac Stuck on the Loading Screen: How to Narrow It Down
A Mac sitting on the Apple logo with a progress bar that has not moved for twenty minutes is the hardest kind of problem to troubleshoot, because the machine cannot tell you anything while it…
“zsh: permission denied” on macOS: The Three Causes and Their Fixes
zsh: permission denied looks like one error, and it is really three. The shell says it when a file has no execute bit, when the thing you pointed at cannot be executed at all, and…
“Disk Not Ejected Properly” on Mac: What Causes It and How to Eject Safely
The “Disk Not Ejected Properly” notification appears after the fact: a volume that macOS still had mounted is suddenly gone. Pulling a cable is the obvious way to cause it, but it also shows up…
Finder Not Responding on Mac: How to Relaunch It and Find the Cause
Finder stops redrawing, the spinning wheel appears, and clicking a window does nothing. Relaunching Finder is the standard first move, and it is safer than force quitting a regular app: Finder is managed by launchd,…
“zsh: command not found” on macOS: Causes and Fixes
When the Terminal prints zsh: command not found: something, it means zsh looked through every directory on your PATH and didn’t find a program by that name. zsh has been the default shell since Catalina…
How to Encode and Decode Base64 on macOS
macOS ships a base64 command at /usr/bin/base64, so there’s nothing to install — it’s the FreeBSD version, which differs from the GNU one on Linux in a couple of ways worth knowing. This covers encoding…
How to Put a Mac in DFU Mode (and Revive or Restore It)
DFU mode is the deepest recovery state on a Mac. DFU stands for Device Firmware Update, and you reach for it in the rare case where a Mac will not turn on, stops at a…
How to Show Hidden Files on a Mac
There is a keyboard shortcut that shows hidden files in the Finder immediately, and for most people that is the entire answer. What trips people up comes after: some files stay out of sight even…