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On most keyboards with two USB plugs, one connects the keyboard to your computer and the other connects the keyboard’s built-in USB pass-through port. The second plug is usually needed to use that port, and on some models it also helps provide power. Whether the keyboard itself works with only one plug depends on the model.
What each plug does
| Connector | Usual role | When you need it |
|---|---|---|
| Main or keyboard plug | Carries the keyboard’s data connection and supplies power to it. | Usually required for the keyboard to work. |
| Pass-through or USB-marked plug | Connects the USB socket built into the keyboard to the computer; depending on the design, it may also provide additional power capacity. | Needed to use the keyboard’s USB socket. Whether it is needed for other keyboard functions varies by model. |
For example, Corsair’s STRAFE RGB MK.2 quick-start guide labels separate “keyboard” and “USB pass-through” connectors. The pass-through socket can be used for a peripheral such as a mouse or receiver.
Do two plugs make the keyboard faster?
Usually, no. Key presses travel through the keyboard’s main USB connection. The second plug is generally for the built-in pass-through port, not extra keyboard bandwidth. Do not assume two plugs mean a higher polling rate, lower latency, or better key rollover; those capabilities are model-specific.
Corsair’s K100 RGB specifications, for instance, list the keyboard’s polling rate separately from its USB pass-through feature. They also identify the pass-through port as USB 2.0 despite the keyboard having two host connectors.
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Do you need to plug in both?
- You want to use the keyboard’s USB socket: Connect both plugs, unless the keyboard’s manual gives different instructions.
- You only need to type: The main plug may be enough on some models, but it is not a universal rule. Check the exact model’s guide.
- The keyboard has two plugs but no obvious pass-through socket: Do not assume one is redundant. Look for labels or symbols and check the manual for that model.
Razer’s support guidance for keyboards with two USB connections recommends connecting both directly to the computer. That is a sensible default when the manufacturer supplies two plugs and does not say one is optional.
A keyboard working with one plug does not prove the other is useless. The keyboard may draw enough power for basic typing from the main connection while the pass-through socket remains inactive, or while an attached device lacks enough power. Features and behavior differ by design.
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Why gaming keyboards may use two plugs
Gaming keyboards can combine large areas of RGB lighting, media controls, macro keys, onboard electronics and a USB pass-through socket. Those features can make the connection and power requirements more involved than those of a basic keyboard. However, the exact reason for a second plug is model-specific: it is commonly associated with pass-through, and may contribute power, but it is not accurate to say every two-plug keyboard uses the plugs in the same way.
As a reference point, standard USB 2.0 downstream ports are limited to 500 mA, while standard USB 3.0 downstream ports can provide 900 mA under the relevant standard. These are standard port limits, not a guarantee of what a particular laptop, dock, monitor hub or charging port will deliver. See the USB-IF compliance guidance. The figures also do not mean that two keyboard plugs simply combine into one larger power supply; the product may use separate power paths or functions.
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How to identify and connect the plugs
- Check for icons or labels on the plugs, cable or keyboard. A keyboard symbol usually marks the main connector; a USB or pass-through symbol may mark the connector for the built-in socket.
- Confirm the labels in the quick-start guide or manual for your exact model. Do not rely only on which plug appears first on the cable.
- Connect the main plug to a USB port on the computer. Connect the second plug to another port on the same computer if you want to use pass-through, or if the manufacturer instructs you to connect both.
- Plug a peripheral into the keyboard’s USB socket and check that it appears in the operating system.
For stability and troubleshooting, direct computer ports are the best first choice. Razer recommends direct connections for the relevant two-connector keyboards, and Corsair’s keyboard troubleshooting guide also advises direct connection in troubleshooting. A powered hub or dock may work if the keyboard supports it, but compatibility and available power vary.
Is the keyboard’s USB socket a full-speed hub?
Treat it as a convenient, potentially limited pass-through port—not as a guaranteed substitute for a computer port or a separate hub. Its speed and power depend on the keyboard. A USB 2.0 pass-through remains USB 2.0 even if the keyboard’s host plugs are connected to USB 3.x ports. It may be fine for a mouse or wireless receiver but a poor choice for an external SSD, a high-power drive, or a device that needs fast charging.
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If you need several peripherals, higher data speeds or more dependable power, a separate powered USB hub may be a better fit. Choose one for the speed and power your devices require, and account for its additional cable and possible bandwidth sharing.
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- Check that the second plug is connected and, if applicable, that both plugs go to the same computer.
- For troubleshooting, connect both plugs directly to the computer rather than through a hub, dock, monitor or KVM switch.
- Try another pair of computer ports.
- Test the mouse, receiver or other peripheral directly in the computer. This helps rule out a fault with the peripheral or its cable.
- Check the keyboard’s specifications for pass-through speed and power limits. A device that needs more power may not work reliably from the keyboard’s socket.
- If the problem persists, follow the exact model’s manual or support instructions. Razer’s pass-through troubleshooting steps include checking both connectors, trying other host ports and testing another device.
What to avoid
- Do not connect the two plugs to different computers. The keyboard’s connections are designed as one system. Keep them on the same host unless the manufacturer explicitly says otherwise.
- Do not assume the second plug is optional just because typing works without it.
- Do not assume the pass-through socket supports fast charging or high-speed storage. Check the model’s specifications or connect demanding devices directly to the computer.
- Do not assume any generic Y-cable is a suitable replacement. A keyboard may have separately wired functions, and USB-IF guidance restricts Y-cable use for USB peripherals. Use only a replacement arrangement approved for the model.
The convenience of a keyboard pass-through port comes at a cost: it uses another host USB port and may be slower or less powerful than a direct connection. If you do not need a nearby socket, you can leave it unused; if you need more ports or stronger power, use a separate hub instead.
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