Brightness keys and shortcuts

How the keys actually work

Pressing a brightness key does not send a normal keystroke. The keyboard controller raises a firmware event, the vendor's driver picks it up, and that driver calls the display control interface. Three components, any of which can be missing — which is why the keys are the first thing to break after a clean install and the last thing to be restored.

The Fn lock trap

Most laptops let you choose whether the function row acts as F1–F12 or as media and brightness keys by default. The setting lives in the firmware, usually as Action Keys Mode or Hotkey Mode, and there is often an Fn + Esc toggle for it. If your keys stopped working after someone else used the machine, check this before anything else.

Restoring dead keys

Install the vendor system utility for your model — this is the component that is missing after a clean install.
Reinstall the vendor display driver rather than the generic GPU package.
In Device Manager, check Keyboards and System devices for entries with warning icons; a failed firmware interface driver disables the whole function row.
If everything is installed and the keys still do nothing, check the vendor utility's own settings — some ship with function-key handling disabled by default.

Shortcuts for external monitors

No laptop key will ever control an external monitor, because the firmware event is wired to the built-in panel. Keyboard control of a desktop display requires a utility that binds a shortcut to a DDC/CI command. This is one of the strongest arguments for installing one: it turns a dive into the monitor's menu into a keystroke.

Choose shortcuts that do not collide. Ctrl + Alt combinations with the bracket keys, or the media keys on an external keyboard, are safer than anything involving Windows + a letter, which Windows itself claims and will win.

Scripted and scheduled changes

Utilities in this category commonly accept command-line arguments, which lets you attach a brightness change to something else — a scheduled task in the evening, a dock event, a shortcut on the desktop. If you already run a scripting layer, this is usually more reliable than a scheduling feature built into a tray app, because Task Scheduler survives the app not being running.