There is no physical fn lock toggle on the Logitech MX Keys keyboard. You must use the Logitech Options+ software to swap the default behavior of the function row, which effectively locks the keys into standard function mode without holding fn.
Why there is no physical lock fn key switch
The Logitech MX Keys was designed around software-based customization rather than hardware-level locking. Many laptop keyboards include a dedicated fn lock key or a fn+Esc toggle. The MX Keys treats the fn key as a modifier. It only temporarily switches the function row between media controls and standard F-keys. Logitech’s engineering decision prioritized a clean, minimal layout. They also wanted consistent behavior across multiple connected devices. The keyboard can pair with up to three devices via the easy switch button on Logitech keyboard. A physical lock would complicate switching between operating systems that handle the function keys on a keyboard differently. The keyboard’s firmware simply lacks the circuitry or memory to store a persistent fn lock state. All such behavior must be managed by the Logitech Options+ software running on your computer.
The software-only workaround
To achieve the locked fn effect, open Logitech Options+ and select your MX Keys from the device list. Navigate to the "Keys" tab. Find the toggle labeled "Use F1-F12 keys as standard function keys." Enabling this setting effectively locks the top row into standard mode. You no longer need to hold the fn key to press F1 through F12. This setting persists across computer restarts and keyboard sleep cycles. It even survives switching between paired devices using the easy switch button. However, this only works while the Logitech Options+ software is installed and running in the background. If you connect the keyboard to a computer without Options+, the fn key will revert to its default behavior. The combination of media controls and standard operations remains accessible, but understanding the difference between toggle and momentary keys helps you adapt quickly, see keyboard keys explained. You simply hold fn to access media keys instead of the other way around.
You must use the Logitech Options+ software to swap the default behavior of the function row. This effectively locks the keys into standard mode without holding fn. The keyboard itself has no dedicated key or button combination that will permanently lock the fn key in place. The shortcut fn+Esc found on many laptops also applies here to toggle the Fn key behavior. The only reliable method is a software setting that persists across reboots and device disconnections.
What people get wrong
The most common confusion occurs when users press fn+Esc expecting a lock indicator light or a persistent mode change. The MX Keys does respond to this combination because it was programmed to toggle the Fn key behavior. The fn key on this model can act as a toggle when used with the Esc key. Another frequent mistake is assuming the hardware is broken when the top-row inputs behave unexpectedly after switching devices or resetting. For example, you might pair your MX Keys with a Windows computer and then switch to a Mac using the easy switch button. The top row may revert because Logitech Options+ settings are per-computer, not stored on the peripheral itself. Additionally, some users confuse the fn key with the command key on a Windows keyboard. They expect it to perform system-level shortcuts like copy and paste. On the MX Keys, the fn key only controls the top row, not modifier commands. Finally, many owners reset the board by unpairing it and then complain that their standard inputs no longer work. They forget that the software setting is not stored onboard. To avoid this, always reapply the "Use F1-F12 keys as standard function keys" toggle in Options+ after any reset or when connecting to a new device.
The Logitech MX Keys may require a persistent background service to maintain a standard function row layout.
