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Function Key Test — Check F1 to F12 and Media Keys

Test every key in the function row, including the media and brightness shortcuts. If F1 to F12 do the wrong thing, this shows whether Fn is the reason.

Function Keys

0/13
Esc
F1
F2
F3
F4
F5
F6
F7
F8
F9
F10
F11
F12

Special Keys

0/9
PrtSc
ScrLk
Pause
Insert
Delete
Home
End
PgUp
PgDn

Why the function row misbehaves more than any other part of a keyboard

The top row is the only part of a keyboard where three separate systems get a say in what a keypress does. The keyboard firmware decides whether the key sends F6 or "volume up". The operating system claims some of what is left — F2 renames a file in Explorer, F1 opens Help. Then the browser claims more still: F5 reloads, F11 goes fullscreen, F12 opens developer tools. By the time a keystroke reaches a web page, several layers have already had the chance to take it.

That is why "my F keys don't work" is usually not a broken keyboard. On most laptops the top row defaults to media and brightness control, and sending an actual F-key requires holding Fn — or toggling Fn Lock so the behaviour inverts. If pressing F5 changes your screen brightness, the switch underneath is working perfectly; the firmware is simply sending a different code.

This page calls preventDefault() on the whole function row, which stops the page-level actions — F5 will not reload while you are testing. A few shortcuts are handled by the browser itself before any page sees them, and no website can cancel those: F12 opening developer tools in Chrome is the usual example. If a key does something instead of lighting up here, that is the reason, and the workaround is in the troubleshooting notes below.

The navigation cluster to the right of the function row has its own quirks. Print Screen is the notable one: on Windows the operating system grabs the press to capture the screen, so browsers commonly report only the release and never the press. Insert does not exist on Mac keyboards at all. If you are working through a full layout rather than just this row, the main keyboard test covers every key at once, and the laptop keyboard test is built around the compact layouts where the function row is most heavily shared.

Key Capabilities & Features

Escape Through F12

Every key in the top row tracked individually, with a running count of how many you have confirmed.

Navigation Cluster Isolated

Print Screen, Scroll Lock, Pause/Break, Insert, Delete, Home, End, Page Up and Page Down tested as their own group.

Page Shortcuts Suppressed

The function row is cancelled at the page level, so F5 will not reload the test out from under you.

Fn Lock Diagnosis

Shows whether your keyboard is sending F-key codes or media codes, which is the actual answer to most F-key complaints.

F13 to F24 Supported

Extended function keys on ergonomic and programmable boards register too, since the listener reads whatever code arrives.

No Install, No Logging

Runs in the page. Keystrokes are handled in browser memory and never transmitted.

How to Perform This Test

  1. Click inside the test card first: browser key events only reach the page when the page has focus, and a stray click on the address bar will send your keystrokes there instead.
  2. Escape and F1 to F4: tap each in turn. If they light up, the keyboard is sending real F-key codes and Fn Lock is set the way you want it.
  3. F5 to F8: press F5 and confirm the page does not reload — that is the shortcut suppression working. F6 and F7 have no browser default to fight.
  4. F9 to F12: F12 may open developer tools despite the suppression, because Chrome handles that one itself. If it does, close the panel and check whether the key registered underneath.
  5. Navigation cluster: tap Print Screen, Scroll Lock, Pause/Break, Insert, Delete, Home, End, Page Up and Page Down.
  6. Read the two counters: both should reach their full count. Anything left dark after a firm press is either shared with an Fn function or genuinely not reporting.

Troubleshooting Common Hardware Issues

  • F keys adjust brightness or volume instead of registering: this is Fn Lock, not a fault. Hold Fn while pressing the key to send the F-code once, or toggle the default. Fn + Esc flips it on most ThinkPad, Dell and Asus laptops; HP and some Acer models set it in the BIOS instead, usually as "Action Keys Mode" or "Function key behavior".
  • Print Screen never lights up on Windows: expected. The operating system intercepts the press to capture the screen, and browsers typically report only the keyup. In Windows 11, Settings › Accessibility › Keyboard also maps it to the Snipping Tool by default, which consumes it earlier still.
  • F12 opens developer tools anyway: Chrome handles that shortcut above the page, so preventDefault cannot reach it. Firefox behaves the same way. Test F12 by watching whether the key registers before the panel opens, or disable the shortcut in your browser settings.
  • The Fn key itself never registers: correct, and not a fault. Fn is resolved inside the keyboard controller or embedded controller and does not send an HID keycode at all, so no software on any operating system can see it.
  • Nothing in the row registers, but ordinary letters do: check for a keyboard utility or gaming profile that has remapped the top row wholesale. Manufacturer software frequently claims the function row for macros.
  • On a Mac, F1 to F12 need Fn by default: change it under System Settings › Keyboard, where "Use F1, F2, etc. keys as standard function keys" inverts the behaviour permanently.

What each function key does by default

Useful context when a key seems to do the wrong thing — often it is doing exactly the right thing for a layer you had forgotten about. Behaviour varies by application; these are the common Windows defaults.

KeyCommon defaultTypical laptop Fn function
F1Open Help in most applicationsMute or help
F2Rename the selected file in ExplorerVolume down
F3Open Find or repeat the last searchVolume up
F4Address bar dropdown; Alt + F4 closes a windowScreen brightness or mic mute
F5Reload the page or refresh a folderBrightness down
F6Move focus between panes; browser address barBrightness up
F7Spell check in Office; caret browsing in FirefoxExternal display toggle
F8Boot menu on some machines during startupKeyboard backlight
F9Refresh fields in Word; send in OutlookWi-Fi or airplane mode
F10Activate the menu bar; Shift + F10 is right-clickMedia previous
F11Toggle browser fullscreenMedia play or pause
F12Open developer tools; Save As in OfficeMedia next

Telling a dead switch apart from a claimed keycode

This is the one distinction worth getting right, because the two problems have completely different fixes and they feel identical from the keyboard.

If the key does something — brightness changes, the volume moves, a panel opens — the switch is fine and the electrical path is fine. Something upstream is claiming the code: firmware via Fn Lock, the operating system, the browser, or a remapping utility. Nothing is broken, and every fix is a setting.

If the key does nothing at all — no light here, no effect anywhere else, in any application — then no code is arriving. That is a hardware problem: debris under the cap, a failed switch, or a break in the matrix. Confirm it in a second application before concluding anything, then work through the physical checks in the stuck key test and the full keyboard test.

A third case catches people out: the key registers here but does nothing in one specific program. That is the program, not the keyboard. Applications bind the function row aggressively, and a plugin or an extension can swallow a key inside a single app while leaving it working everywhere else.

Frequently Asked Questions

Why do my F keys control brightness or volume instead of F1 to F12?
Most laptops ship with the top row defaulting to media and brightness, because that is what people reach for more often. The switch is working correctly — the firmware is simply sending a different code. Hold Fn while pressing the key to send the F-code once. To invert the default permanently, try Fn + Esc, which toggles Fn Lock on most ThinkPad, Dell and Asus machines; HP and some Acer models put the setting in the BIOS instead, under a name like "Action Keys Mode".
Why does my Print Screen key never register?
Because Windows takes the press before the browser sees it, in order to capture the screen. Browsers commonly report only the keyup for Print Screen and never the keydown, so the key can look dead while working perfectly. Windows 11 adds a second layer: Settings › Accessibility › Keyboard maps Print Screen to the Snipping Tool by default, which consumes the press earlier still.
Can this test detect F13 through F24?
Yes. The HID specification defines usage codes for F13 to F24, browsers report them as ordinary key codes, and the listener on this page reads whatever arrives rather than a fixed list. Programmable boards running QMK or VIA, and extended Mac keyboards with F13 to F19, will register normally — they just will not have a labelled square in the grid above.
Why does the Fn key itself never light up?
Fn is not a keycode. It is resolved inside the keyboard controller, or on a laptop inside the embedded controller, which then decides which code to send for the key you pressed alongside it. Because nothing is transmitted for Fn on its own, no operating system or website can detect it. This is by design and identical across Windows, macOS and Linux.
Why does F12 still open developer tools when the page blocks it?
Some shortcuts are handled by the browser above the page, so a website calling preventDefault never gets the chance to cancel them. F12 in Chrome and Firefox is the common example, and F11 fullscreen behaves similarly. It is a deliberate security boundary rather than a bug. You can still see whether the key registered by checking the grid after closing the panel.
What is the Pause/Break key for?
It began as a way to pause scrolling terminal output and interrupt DOS commands. It survives mostly as a shortcut key — on Windows, Ctrl + Pause is still an interrupt in some consoles, and the key is often the fastest route to system information. Many compact and laptop keyboards have dropped it entirely or moved it behind Fn.
Does this test work on Mac function keys?
Yes. On macOS the top row sends media codes by default, so hold Fn while pressing to send F1 to F12, or change it under System Settings › Keyboard with "Use F1, F2, etc. keys as standard function keys". Note that Mac keyboards have no Insert key, and the key labelled Delete is Backspace — forward delete is Fn + Delete.
My function keys work here but not in one application. What now?
Then the keyboard is fine and that application is claiming the key. The function row is the most heavily bound part of the keyboard, and a plugin, extension or accessibility feature can swallow a key inside one program while leaving it working everywhere else. Check that application's own keyboard shortcut settings first.

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