COOLER MASTER CK721 - Keyboard

CK721 - Keyboard COOLER MASTER - Free user manual and instructions

Find the device manual for free CK721 COOLER MASTER in PDF.

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Product type Wireless mechanical keyboard
Brand Cooler Master
Model CK721
Form factor 75% with arrow keys and integrated numeric keypad
Connectivity Bluetooth 5.1, 2.4 GHz wireless (included dongle), USB-C wired
Power supply Rechargeable lithium-ion battery (typical capacity 4000 mAh)
Announced battery life Up to 200 hours (backlight off)
Backlighting Per-key RGB, customizable effects via Cooler Master software
Dimensions (approx.) 31.5 × 12.0 × 4.0 cm
Weight (approx.) 800 g
Material ABS plastic chassis, double-shot PBT keycaps, hot-swappable
Compatibility Windows, macOS, Android, iOS, Linux
Main features Switching between 3 Bluetooth devices, 2.4 GHz and wired mode, FN multimedia keys, Windows key lock
Maintenance and cleaning Use a soft, slightly damp cloth; do not use solvents or abrasive cleaners. Unplug before cleaning.
Safety Do not expose to moisture or extreme temperatures. Do not open the housing. Use only the provided cable.
Spare parts and repairability Hot-swappable keycaps and switches. Standard USB-C cable available. Battery replaceable by a professional.
Warranty 2 years (according to local legislation)

Frequently Asked Questions - CK721 COOLER MASTER

How to connect the keyboard via Bluetooth?
Slide the switch on the side to Bluetooth mode. Use the combination FN + DEL/PGUP/PGDN for 5 seconds to pair. The indicator flashes blue. On your device, search for 'CK721' in Bluetooth devices.
How to switch to 2.4 GHz mode?
Switch the switch to 2.4 GHz mode. Plug the included dongle into a USB port on your computer. The keyboard connects automatically. The indicator turns solid green for 3 seconds if the connection is successful.
How to charge the battery?
Connect the keyboard to a USB port via the provided USB-C cable. The indicator turns red while charging. Once the battery is full, the indicator turns green. A full charge takes about 2 to 3 hours.
What to do if the keyboard does not power on?
Check that the battery is not discharged. Connect the USB cable to recharge. If the problem persists, reset the keyboard by holding FN + R for 5 seconds.
How to switch between multiple Bluetooth devices?
Use FN + DEL (device 1), FN + PGUP (device 2), or FN + PGDN (device 3) to change the connected device.
The indicator flashes red, what does it mean?
A red flashing indicator every 20 seconds indicates low battery (less than 15%). Recharge the keyboard as soon as possible.
How to customize RGB effects?
Download and install the Cooler Master MasterPlus software or use FN shortcuts: FN + arrows to change mode, FN + function keys for brightness.
The keyboard is unresponsive, how to reset it?
Hold FN + R for 5 seconds. The keyboard will restart to factory settings.
Can I replace the switches?
Yes, the CK721 supports hot-swappable switches (3-pin). Carefully remove the keycap and switch using the included tool or a compatible puller.
How to clean the keyboard?
Unplug the keyboard. Use a soft, slightly damp cloth (water) to wipe the surface. For areas between the keys, a compressed air blower or a soft brush is recommended.

User questions about CK721 COOLER MASTER

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My COOLER MASTER CK721 keyboard lights up but doesn't type anything - how to fix it?
Frequently Asked Questions - 30/05/2026
Response Notice-Facile

If your CK721 keyboard lights up (the LEDs activate) but the keys do not send any characters to your computer, this generally indicates a connection issue or a loss of synchronization. Here’s how to diagnose and fix it:

1. Check the active connection mode

The CK721 supports three modes: Bluetooth, 2.4GHz wireless (with dongle), and USB-C wired. If you were using Bluetooth and nothing works, the keyboard may have disconnected.

  • Bluetooth Mode: Press FN + DEL/PGUP/PGDN for 5 seconds to restart pairing. The indicator should blink blue (3 times per second) - that's a good sign.
  • 2.4GHz Mode: Reinsert the USB dongle into your computer. The connection should establish automatically.
  • Wired Mode: Plug the USB-C cable directly into your PC to test if the keyboard responds in wired connection (no battery used).

2. Low or uncharged battery

Even if the LEDs light up, a very low battery can prevent keyboard data transmission. Fully charge the CK721 by connecting the USB-C cable: the indicator turns red while charging, then green once charged (2-3 hours for a full charge).

3. Reset the keyboard

If none of the above tests work, a factory reset will restore the connection:

  • Hold FN + R for 5 seconds
  • This resets all Bluetooth pairings and restores default settings
  • Then, reconnect via Bluetooth or 2.4GHz as during installation

If after these steps the keyboard still lights up but the keys remain unresponsive, there may be a hardware issue with the switches or the detection circuit. In this case, contact COOLER MASTER for diagnosis or replacement.

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How to reset the COOLER MASTER CK721 to factory settings?
Frequently Asked Questions - 30/05/2026
Response Notice-Facile

To reset the COOLER MASTER CK721 to factory settings, follow these steps:

Press and hold the FN + R keys simultaneously for 5 seconds.

The keyboard will automatically restart and return to its default factory settings. This operation will erase all previous Bluetooth pairings and reset the RGB backlight settings.

You will see a flashing blue light for a few seconds, followed by a steady green light (for 3 seconds) to confirm that the reset was successful and the keyboard is ready to be configured again.

This procedure is useful if the keyboard is not responding correctly or if you want to pair it with another device without keeping the old pairings.

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Download the instructions for your Keyboard in PDF format for free! Find your manual CK721 - COOLER MASTER and take your electronic device back in hand. On this page are published all the documents necessary for the use of your device. CK721 by COOLER MASTER.

USER MANUAL CK721 COOLER MASTER

CK721 WIRELESS SETUP GUIDE

EN

IMPORTANT

Please charge your new keyboard for at least 2 hours before using for the first time.

A. USING BLUETOOTH - AN OVERVIEW

COOLER MASTER CK721 - IMPORTANT - 1

COOLER MASTER CK721 - IMPORTANT - 2

B. MANUALLY PAIRING DEVICES

TO THE KEYBOARD

COOLER MASTER CK721 - IMPORTANT - 3

C. SWITCH PAIRED DEVICES

COOLER MASTER CK721 - IMPORTANT - 4

A. USING 2.4 GHZ - AN OVERVIEW

COOLER MASTER CK721 - IMPORTANT - 5

COOLER MASTER CK721 - IMPORTANT - 6

B. MANUALLY PAIRING 2.4 GHZ DONGLE

TO THE KEYBOARD

COOLER MASTER CK721 - IMPORTANT - 7

BLUETOOTH MODE

  1. Isolate the pharyngeal switch on the side of
  2. Press and hold FN + DEL/PGUP/PGDN for 5 seconds to enter pairing mode. The Indicator & DEL/PGUP/PGDN key will rapidly flash BLUE 3 times one every second to confirm you are in Pairing Mode.
  3. If pairing is successful, the indicator & DEL/PGUP/PGDN key will light up with a solid GREEN light for 3 seconds. If unsuccessful, the keyboard will enter Sleep Mode after 30 seconds. In Sleep Mode, all the keyboard lighting will be turned off.

Turning On Bluetooth After the First Time

  1. When the Bluetooth mode is activated, the keyboard will connect to the previous

  2. If successfully connected, the Indicator & DEL/PGUP/PGDN key will light up with a solid GREEN light for 3 seconds. If unsuccessful, the keyboard will enter Sleep Mode and turn off the LED. The LED will then turn on again.

  3. To connect to a specific paired device, press FN + DEL/PSUP/PGDN after activating Bluetooth mode to connect to the corresponding device. The keyboard will connect to the device if successful and enter sleep mode after 30 seconds if device is not found or fails to connect.

  4. Toggle the physical switch on the side of the keyboard to enter Bluetooth Mode. 2. Press and hold FN + DEL/PGUPU/PCDN for 5 seconds to enter pairing mode. The Indicator & DEL/PGUPU/PCDN key will rapidly flash BLUE 3 times one every second to confirm you are in pairing mode.

  5. If passing is successful, the indicator & DH/PEG/UPGON key will light up with a green light and the keyboard will turn off. The indicator & DH/PEG/UPGON key will turn off after 30 seconds. In Sleep Mode, all the keyboard lighting will be turned off.

  6. Press FN + DEL/PGUP/PGDN to switch to the corresponding paired device

2.4 GHz MODE

  1. Toggle the physical switch on the side of the keyboard to enter 2.4 GHz Mode. The Indicator & Enter key will continuously flash a BLUE light one every second to confirm it is trying to connect to a device.
  2. Plug the included dongie into the desired device. The keyboard will automatically send the dongie to the device.
  3. If successfully connected, the Indicator & Enter key will light up with a solid GREEN light for 3 seconds. If unsuccessful, the keyboard will enter Sleep Mode after 30 seconds. In Sleep Mode, all the keyboard lighting will be turned off.
  4. To pair with other devices, simply unplug the dongle and re-plug into another device. If pairing is successful, the Indicator & Enter key will light up with a solid GREEN light for 3 seconds. If unsuccessful, the LED will turn off and the device will be turned off in seconds. In Sleep Mode, all the keyboard lighting will be turned off.
  5. Toggle the physical switch on the side of the keyboard to enter 2.4 Glitz Mode. Press and hold PN + Enter for 5 seconds to enter pairing mode. The indicator & Enter key will rapidly flash BLUE 3 times one every second to confirm you are in Pairing Mode.
  6. Plug the Included dongle into the desired device, The keyboard should automatically connect to the device.
  7. If pairing is successful, the indicator & Enter key will light up with a solid GREEN light for 3 seconds. If unsuccessful, the keyboard will enter Sleep Mode after 30 seconds. In Sleep Mode, all the keyboard lighting will be turned off.

SWITCHING TO WIRED MODE

COOLER MASTER CK721 - GHz MODE - 1

CHARGING THE KEYBOARD

COOLER MASTER CK721 - GHz MODE - 2

A. CAPSLK Indicator

COOLER MASTER CK721 - GHz MODE - 3

B.Wireless Mode

COOLER MASTER CK721 - GHz MODE - 4

C. Low Battery Scenario

COOLER MASTER CK721 - GHz MODE - 5

D. Indicator on DEL/PGUP/PGDN

COOLER MASTER CK721 - GHz MODE - 6

WIRED MODE

If the physical switch is toggled to Bluetooth or 2.4 GHz Mode The keyboard will switch to Wired Mode automatically as the physical switch is toggled to Wired and it is connected to a PC or laptop.

If the physical switch is toggled to Wired Mode

The keyboard will switch to Wired Mode automatically as it is connected to a PC or laptop.

CHARGING

If the physical switch is toggled to Bluetooth or 2.4 GHz Mode The keyboard will remain connected to the wireless device and begin charging when it is plugged into a PC, laptop, or power source. When charging, the indicator light will be RED and the keyboard will light up with RED BREATHING lights then switch back to the GREEN mode. When the battery level is full, the Indicator light will change to GREEN and the keyboard will light up with GREEN BREATHING five times.

If the physical switch is toggled to Wired Mode

The keyboard will begin charging when it is plugged into a PC, laptop, or power source. When charging, the indicator light will be RED and the keyboard will light up with RED BREATHING five times then switch back to light mode.
When the battery level is full, the indicator light will change to GREEN for 3 seconds then turn off and the keyboard will light up with GREEN BREATHING five times.

INDICATOR LIGHT RULE

The CAPSLK indicator will light up with a solid WHITE light when turn on CAPSLK key, and turn off when turn off CAPSLK key.

  1. In Paing Mode, the Indicator & DEL/PGUP/PSDN key will rapidly flash BLUE 3 times one every second.

  2. In Connecting Mode, the indicator & DEL/PGUP/PGON key will continuously flash a BLUE light once every second.

  3. If Connecting / Connecting is successful, the indicator & DEL/PGUP/PGDN key will light up with a solid GREEN light for 3 seconds.

  4. When the battery level falls below 15%, the keyboard will enter Low Power Mode and the keyboard backlight will be turned off. The indicator will repeatedly flash RED light 3 times every 20 seconds until the keyboard enters Sleep Mode or is connected to the PC, laptop or power source.

The Low Power Mode percentage can be customized via Cooler Master software.

  1. When the battery level falls below 5% , the keyboard will go into Deep Sleep Mode. All lighting will be turned off - including the indicator.

Press FN will show the pairing status of each location (DEL, PGUP or PGDN) with WHITE light.

WICHITG

© 2021Cooler Master Technology Inc. All Rights Reserved. All trademarks are registered to their respective owners. Ver 1.0: 2021/02 512004490-GP

COOLER MASTER CK721 - WICHITG - 1

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Product information

Brand : COOLER MASTER

Model : CK721

Category : Keyboard