If your MacBook’s F1–F12 keys aren’t doing what you expect—brightness and volume stopped working, or F5 opens a menu instead of refreshing a page—it is almost never a broken keyboard. In 90% of cases it is one setting. Here is the fast fix, then the less common causes, and finally how to tell a setting problem from a real hardware fault.
First, understand what the Fn key actually does
On every modern Mac keyboard the top row is dual-purpose. Each key is both a media control (brightness, volume, Mission Control, Spotlight) and a standard function key (F1, F2, F3…). The Fn key (bottom-left, labeled Fn or with a globe icon 🌐 on newer models) is what switches between the two behaviors.
- Default: pressing F1 lowers brightness. Holding Fn and pressing F1 sends a real “F1” to the app.
- You can flip that default so F1 is always “F1” and you hold Fn to get brightness. That single toggle is what most people are actually looking for.
The one setting that fixes most “Fn key not working” complaints
Open Apple menu ▸ System Settings ▸ Keyboard. Click Keyboard Shortcuts… (bottom right), then select Function Keys in the sidebar.
- Turn “Use F1, F2, etc. keys as standard function keys” ON if you want F-keys to send real F1–F12 (great for Excel, Windows remote sessions, and IDEs). Brightness/volume then require holding Fn.
- Turn it OFF to get one-press brightness, volume, and media controls back.
On older macOS this lives at System Preferences ▸ Keyboard ▸ Keyboard as the checkbox “Use F1, F2, etc. keys as standard function keys.” Flip it to whichever behavior you expected and the “broken” F-keys will come right back.
The Fn / Globe key does more than function keys
On recent MacBooks the Fn key is also the Globe key, and pressing it can trigger an action you did not mean to—like switching input sources or opening the emoji picker. Set what it does under System Settings ▸ Keyboard ▸ “Press 🌐 key to” and choose Do Nothing, Change Input Source, Show Emoji & Symbols, or Start Dictation. If your Fn key “does something weird,” this menu is the cause.
Still not working? Run down this list
- Restart the Mac. A stuck modifier state after sleep or a crashed app is the single most common transient cause.
- Check for a stuck or dirty key. If Fn feels mushy or does not click, a crumb under it can hold it “pressed.” Blow it out with compressed air.
- Test in another app. Some apps remap F-keys (Excel uses F2/F4; browsers use F5/F11; screen-share tools grab function keys). If F-keys work on the Desktop but not in one app, it is that app’s shortcuts, not your keyboard.
- Turn off Mouse Keys. System Settings ▸ Accessibility ▸ Pointer Control—if Mouse Keys is on, part of the keyboard drives the pointer instead of typing.
- Boot in Safe Mode (hold Shift on Intel; hold the power button on Apple silicon and choose the startup disk with Shift). If the Fn key works in Safe Mode, a login item or a third-party keyboard tool (Karabiner-Elements, BetterTouchTool) is intercepting it.
- Disconnect external keyboards and test the built-in one alone to isolate the fault.
Fn-lock on an external or Windows keyboard
Using a PC or third-party keyboard? Many have their own Fn Lock (often Fn + Esc, or a padlock icon on a key) that flips the top row independently of macOS. If only an external keyboard is affected, toggle its Fn Lock first, then set macOS to match under Keyboard ▸ Function Keys.
How to tell a setting from a real hardware fault
It is a setting (fixable in two minutes) if:
- The keys still do something—just the wrong thing (F-keys instead of brightness, or vice-versa).
- The behavior is consistent across restarts.
- It changed right after a macOS update or plugging in a new keyboard.
It may be hardware if the Fn key or F-row is completely dead, feels physically stuck, or a cluster of nearby keys stopped registering together—classic on the 2015–2019 butterfly keyboards. If several keys fail as a group, see our guide on a MacBook keyboard not working and keys repeating or double-typing.
If it is the keyboard, get a number before you pay to repair it
A butterfly-era keyboard repair can run into the hundreds, which is often more than an older MacBook is worth. Before you spend it, find out what the machine is worth as-is—working or not. We buy MacBooks in any condition, and you can get a trade-in number on a broken MacBook in a couple of minutes. If it is time to upgrade instead, our Apple clearance MacBooks start at $450, all tested and warrantied.
Frequently Asked Questions
Why do my F-keys change brightness instead of acting as F1, F2?
That is the Mac default. Turn on System Settings ▸ Keyboard ▸ Keyboard Shortcuts ▸ Function Keys ▸ “Use F1, F2, etc. keys as standard function keys.” Then hold Fn when you want brightness or volume.
Where is the Fn key on a MacBook?
Bottom-left corner of the keyboard. On newer models it is labeled with a globe 🌐 icon and doubles as the Globe key.
My Fn key does nothing at all—is it broken?
Restart first, then test in Safe Mode. If Fn works in Safe Mode, a third-party keyboard app is intercepting it. If it is dead everywhere and feels stuck, it is likely a hardware fault—common on 2015–2019 butterfly keyboards.
How do I lock the function keys so I don’t have to hold Fn?
On the built-in Mac keyboard, turn on “Use F1, F2, etc. keys as standard function keys” (above). On an external keyboard, use its own Fn Lock, usually Fn + Esc.
Related: How to remap modifier keys on a Mac · Mac keyboard shortcuts for beginners · All guides →