OpenFlow
Keyboard tester
Press any key and watch it light up. Includes the honest truth about testing the fn key in a browser, and the trick that actually works.
Live event log
The newest keypress is on top. key is the character produced, code is the physical key.
Why the fn key does not light up
macOS handles fn at the hardware and system level and never hands it to browsers as a key event. That is not a bug in this tester, and no web page can show it directly. But you can still prove it works.
If fn opens the emoji picker instead, macOS has it bound to the globe key. Open System Settings, go to Keyboard, and set "Press globe key to" to Do Nothing. That frees fn for apps that use it as a hotkey.
Testing fn because your dictation hotkey died? If you use OpenFlow, switching input devices or waking from sleep no longer kills the hotkey as of v0.2.2. And if fn does nothing anywhere, check the globe key setting above. More about OpenFlow.
Questions people ask
Why does the fn key not show up in online keyboard testers?
macOS handles fn at the hardware and system level and never delivers it to browsers as a key event, so no web page can see it directly. You can still prove it works: hold fn and press the left arrow. If the page receives Home instead of ArrowLeft, your fn key is doing its job.
How do I test if a key is broken?
Press it on the layout above. If it never lights up and nothing appears in the event log, the browser is not receiving it at all, which usually means a hardware fault or a stuck key. Test the same key in another app first to rule out one misbehaving program.
What is the difference between key and code?
The key value is the character produced, which changes with your layout and with modifiers (shift plus 1 gives an exclamation point). The code value is the physical key position and never changes, so KeyA is the same physical key on QWERTY and AZERTY. Use code when you care about the physical key, key when you care about the character.
My fn key opens the emoji picker instead of doing its job. How do I fix it?
Open System Settings, go to Keyboard, and change "Press globe key to" from Show Emoji to Do Nothing. macOS assigns the emoji picker to fn (the globe key) by default, which intercepts it before other apps can use it as a shortcut.
One key. That is the whole interface.
OpenFlow turns the key you just tested into dictation anywhere on your Mac. Hold it, talk, release, and your words appear at the cursor, transcribed entirely on device. Free and open source.
Apple Silicon, macOS 14 or later. Pick fn or any hotkey you like.