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At the moment I'm trying to remote control my machine and command and ctrl do not seem to be working properly. Is there some type of 'keyboard sniffer' functionality so I can see exactly what is and is not being received?

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  • I was looking for the same thing, It's called "keystroke visualizer". Dec 1, 2015 at 0:20

3 Answers 3

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I don't know if the built-in keyboard viewer is sophisticated enough, but it should highlight pressed keys.

If you do not see those options, make sure it is checked off under your System Preferences > Keyboard

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There are also apps like Keycastr that display bezel elements for pressed keys.

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  • no need in terminal. need octal/hex numbers. otherwise you don't know what is being sent.
    – mathtick
    Mar 2, 2019 at 12:51
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    In 10.15.5 this checkbox appears to be moved to Preferences -> Keyboard -> Input Sources -> "Show Input menu in menu bar"
    – mathandy
    Jun 20, 2020 at 2:18
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The application Key Codes from Many Tricks, available for free from the App Store, displays the key code, unicode value, and modifier keys state for any key combination pressed on your computer. If you need more extensive information than that provided by the Keyboard Viewer, you might find it helpful.

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    I tried Key Codes and it doesn't work for media keys.
    – Dan Mandle
    Mar 11, 2015 at 22:20
  • This is exactly what I needed to debug a firmware of int'l keyboard.
    – epx
    May 18, 2019 at 2:22
  • Let's try on macOS.
    – Smeterlink
    May 20, 2020 at 23:21
  • As @epx highlights, this is very helpful for alternative keyboard layouts, including Dvorak. Mar 27 at 14:16
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Karabiner Elements includes an Event Viewer that works really well. For example, Apple's Keyboard Viewer just ignores keypad keys; Karabiner-EventViewer shows them.

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