Apple Resources - Diagnostics

Use Apple Diagnostics to test your Mac   

  If you think your Mac might have a hardware issue, you can
  use Apple Diagnostics to help determine which hardware
  component might be at fault. Apple Diagnostics also suggests
  solutions and helps you contact Apple Support for

EtreCheckPro (free) - for power users

CleanMyMac X (not free, but excellent)   

  CleanMyMac X is all-in-one package to awesomize your Mac. It
  cleans megatons of junk and makes your computer run faster.
  Just like it did on day one.

Malwarebytes (free)   

  Proven Malwarebytes technology crushes the growing threat
  of Mac malware, including thorough malware, spyware, and
  virus removal. Finally, cybersecurity smart enough for
  the Mac.


CONNECTIVITY Connectivity (internet) WiFi Connectivity

SCREEN SHARING Share your screen using Messages on Mac Share the screen of another Mac One important capability available to Mac owners is the ability to screen share between any two Mac computers over the internet. With the permission of both parties the initiator can share remote owner's screen, sound and cursor function. Siri "Launch Screen Sharing"

DFU (User Beware) Everything You Need to Know - DFU Mode for iOS/iPadOS Devices The DFU Mode in iPhones and iPads is an emergency tool that's not designed for most people to ever see. It's hard to activate, and the screen stays blank when you finally manage to trigger it. And yet this obscure tool is essential for resurrecting a dead iPhone, or rolling back an unwanted iOS update. DFU Mode is more powerful than Recovery Mode, and is unsupported and undocumented for us, the end user. It lets an iOS device connect and talk to iTunes (or its Finder equivalent in macOS Catalina), without loading the bootloader, or iOS itself. As its full name - Device Firmware Update Mode - suggests, the mode is used to update the actual firmware of the device, mostly to install a boot loader. DFU Mode is hard to enter, requiring convoluted sequences of button presses to enter. Even when you reach DFU Mode, the screen remains blank. Unlike recovery mode, which can be updated with a software update, DFU is burned into the hardware, and cannot be altered. But it's a powerful tool. Because it works at a lower level than Recovery Mode, DFU lets you do things not allowed in Recovery Mode.