What the Fn key does
Fn is a modifier handled by the keyboard's own firmware. Held with another key it triggers the secondary function printed on that key: brightness, volume, media controls, and on laptops without a numpad, keys like Home, End, Page Up, Page Down, Insert and Print Screen.
Because Fn is processed inside the keyboard, the operating system never sees it. That is why a keyboard tester cannot show Fn being pressed, and why you cannot remap it in normal software.
On a Mac
On Apple keyboards Fn toggles the function row between media controls and F1 to F12. A single tap of the globe/Fn key opens the emoji picker (or switches keyboard language, configurable in System Settings → Keyboard). Fn+Delete is forward delete and Fn+arrows are Home, End, Page Up and Page Down.
On a laptop
Many laptops have an "Fn Lock" (Fn+Esc or a padlock icon) that swaps the default behaviour of the F-row between media keys and F1–F12. If your F keys do the wrong thing, toggle Fn Lock or change the setting in the BIOS/UEFI or the manufacturer's keyboard utility.
Shortcuts that use the Fn key
| Shortcut | What it does |
|---|---|
| Fn+F1…F12 | Brightness, volume, media and airplane mode on most laptops |
| Fn+Esc | Toggle Fn Lock on many laptops |
| Fn+Delete (Mac) | Forward delete |
| Fn+Left / Right (Mac) | Home / End |
| Fn+Up / Down (Mac) | Page Up / Page Down |
| Fn (tap, Mac) | Open the emoji picker |
If the Fn key is missing or not working
If Fn seems broken, remember it never appears in software testers. Check Fn Lock first, then the keyboard settings in the manufacturer's utility or BIOS. On a Mac, System Settings → Keyboard controls what Fn does.
Test it here: click the tester, press the key, and it should light up green. A red key is stuck; a key that never lights up is dead or intercepted by the system. The full keyboard tester has the press log and more detail.
Click the tester, then press any key. Browser shortcuts are blocked while it has focus.
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- key
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- code
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- keyCode
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none
Max at once: 0 (rollover)
None detected. A key held for more than 2 seconds is flagged.
Frequently asked questions
What does the Fn key do? +
It activates the secondary function printed on another key, such as brightness or volume on the F row, or Home and End on the arrow keys of a laptop.
Why is the Fn key not showing up in a keyboard tester? +
Fn is handled by the keyboard hardware and never sent to the computer as a key press. Only the resulting key (for example F5 or Home) reaches the operating system.
How do I turn off Fn Lock? +
Press Fn+Esc on most Dell, Lenovo and HP laptops, or look for a padlock icon on one of the keys. Otherwise change the "Function key behaviour" setting in the BIOS or the maker's utility.
Where is the Fn key on a Mac? +
Bottom-left corner. On recent MacBooks it doubles as the globe key that opens the emoji picker when tapped on its own.