On a Mac the function (Fn) keys on macOS changes the screen’s brightness, activate Misson Control, toggle Spotlight, and toggles mute.
By using Karabiner-Elements you can customize keys, including the behavior of Fn depending on the app currently in use.
Excel users might want F2 as a shortcut to edit a cell. VS Code users may want F5 to start debugging
Below are two examples created using the Karabiner Complex Modification online tool.
# Install Karabiner Elements for macOS Keyboard Key Re-Mapping: https://karabiner-elements.pqrs.org/docs/
brew install --cask karabiner-elements
# Create a Karabiner Complex Rule to map F1 and F2 keys for Chrome and Excel (more for F2 to edit a cell)
# Edit the rule here: https://genesy.github.io/karabiner-complex-rules-generator/#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
open 'karabiner://karabiner/assets/complex_modifications/import?url=data:application/json;charset=utf-8;base64,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'
# Create a Karabiner Complex Rule to map F5 for VS Code
# Edit the rule here: https://genesy.github.io/karabiner-complex-rules-generator/#eyJ0aXRsZSI6IlZTIENvZGUgS2V5bWFwcGluZyIsInJ1bGVzIjpbeyJkZXNjcmlwdGlvbiI6IkY1PUY1IiwibWFuaXB1bGF0b3JzIjpbeyJ0eXBlIjoiYmFzaWMiLCJmcm9tIjp7Im1vZGlmaWVycyI6eyJvcHRpb25hbCI6WyJhbnkiXX0sImtleV9jb2RlIjoiZjUifSwiY29uZGl0aW9ucyI6W3sidHlwZSI6ImZyb250bW9zdF9hcHBsaWNhdGlvbl9pZiIsImJ1bmRsZV9pZGVudGlmaWVycyI6WyJjb20ubWljcm9zb2Z0LlZTQ29kZSJdfV0sInRvIjpbeyJyZXBlYXQiOnRydWUsImtleV9jb2RlIjoiZjUifV19XX1dfQ==
open 'karabiner://karabiner/assets/complex_modifications/import?url=data:application/json;charset=utf-8;base64,eyJ0aXRsZSI6IlZTIENvZGUgS2V5bWFwcGluZyIsInJ1bGVzIjpbeyJkZXNjcmlwdGlvbiI6IkY1PUY1IiwibWFuaXB1bGF0b3JzIjpbeyJ0eXBlIjoiYmFzaWMiLCJmcm9tIjp7Im1vZGlmaWVycyI6eyJvcHRpb25hbCI6WyJhbnkiXX0sImtleV9jb2RlIjoiZjUifSwiY29uZGl0aW9ucyI6W3sidHlwZSI6ImZyb250bW9zdF9hcHBsaWNhdGlvbl9pZiIsImJ1bmRsZV9pZGVudGlmaWVycyI6WyJjb20ubWljcm9zb2Z0LlZTQ29kZSJdfV0sInRvIjpbeyJyZXBlYXQiOnRydWUsImtleV9jb2RlIjoiZjUifV19XX1dfQ=='