A Media key is a key with a special purpose for a specific type of applications or operating system functions. Normally, these functions are concerned with media playback, but the term has been used for other functions as well.
A media key can be a dedicated key, or another key can act like a media key in conjunction with the Fn key. Some USB keyboards contain also a knob or roller, usually for volume control.
On many keyboards, media keys are dedicated keys with no other function.
On the Apple aluminium keyboards with MacOS, the default behaviour is the reverse: numbered function keys are available on the media keys when holding down Fn. This behaviour can be switched in MacOS.
On some PC keyboards from Microsoft, the Fn "key" is not a modifier key but a toggle switch.
|Apple Aluminium Keyboard A1243||Brightness Down||Brightness Up||Exposé / Mission Control||Dashboard / Launchpad||Rewind (Previous track)||Play/Pause||Fast Forward (Next track)||Mute||Volume Down||Volume Up||Eject, F13..F19|
|Arachnid Recore||Play/Pause||Stop||Previous track||Next track||Media player||Mute||Volume Down||Volume Up|
|CMStorm QuickFire Rapid||Play/Pause||Stop||Previous track||Next track||Mute||Volume Down||Volume Up|
|Ducky G2Pro/Shine||Mute||Volume Down||Volume Up||Play/Pause||Stop||Previous track||Next track||Calculator Computer Email Home/Browser|
|iOne (Func KB-460, QPad MK-50 etc.)||Mute||Volume Down||Volume Up||Play/Pause||Previous track||Next track|
|KeyCool 84, KeyCool 87||Computer||Home/Browser||Calculator||Media Player||Previous Track||Next Track||Play/Pause||Stop||Mute||Volume Down||Volume Up||(Windows lock)|
|KeyCool 108||Computer||Home/Browser||Media Player||Previous Track||Next Track||Play/Pause||Stop||Mute||Volume Down||Volume Up||(Windows lock)||Lock Sleep, Calculator, ... ?|
|Matias Quiet Pro Mini (PC)||Rewind (Previous track)||Forward (Next track)||Play/Pause on Esc, Mute Volume Up/Down on Fn-Arrow key|
|Max Keyboard Blackbird||Mute||Volume Down||Volume Up||Play/Pause||Previous Track||Next Track|
|Mionix Zibal 60||Mute||Volume Down||Volume Up||Play/Pause||Stop||Previous Track||Next Track|
|Noppoo Lolita||My Computer||Web Browser||Calculator||Media Player||Previous Track||Next Track||Play/Pause||(NKRO)||Mute||Volume Down||Volume Up|
|Noppoo Lolita Spyder||Previous Track||Play/Pause||Next Track||Stop||Mute||Volume Down||Volume Up|
|Plum 96||Mute||Volume Down||Volume Up||Play/Pause||Previous Track||Next Track||Home/Browser||My computer||(Debounce dec)||(Debounce inc)|
|SteelSeries 6GV2||Mute||Volume Down||Volume Up||Play/Pause||Previous Track||Next Track|
Media keys usually emit distinct codes to the host.
In the USB HID ("Human Interface Device") standard, while most key codes are in the "Keyboard/Keypad" usage page (0x07), most most media keys are in "Consumer" usage page (0x0C). System control keys (Power, Sleep, Wake) are in the "Generic Desktop" usage page (0x01).
The "Consumer Usage Page" has also codes for linear relative values for volume control, bass and treble. While it may appear to be analogue, the knob or roller is usually connected to a rotary encoder. The values are relative to the volume level set by the user in the operating system and application software. If the controls had absolute values, they would have needed to be motorized and under computer control, which is something that the USB HID specification does not support.
The controls in each Usage Page are transmitted in a separate packet. Therefore, media keys may have separate rollover characteristics from regular keys.
Some vendors have used their own codes that have been activated first after having received a "magic" code from the host's keyboard driver.