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A jumper cap is a small removable conductive bridge that fits over designated header pins to select a hardware setting. When it connects the pins specified by a device’s manual, it closes that circuit; removing it opens the circuit. Its meaning depends on the particular board, so never infer a setting from the cap’s position alone.
What a jumper cap does
A jumper header exposes metal pins connected to a circuit. The cap—also called a shunt jumper—contains a conductive contact that joins the pins it covers. That connection changes a hardware configuration supported by the device; it is not a software setting. Supermicro describes jumpers as creating shorts between two pins to change a connector’s function in its X14SBHM jumper-settings documentation.
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How to read jumper positions
Two-pin headers
On a two-pin header, a cap covering both pins is usually described as closed; with the cap removed, the pins are open. Those terms describe the electrical connection, not whether the device is powered on. Supermicro defines the terms this way in its X14SBHM manual.
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A three-pin header can offer two positions: the cap bridges one adjacent pair or the other. The manual specifies which pair selects which state. For example, a Supermicro motherboard-connection diagram depicts the cap spanning a pair of pins, while its accompanying documentation identifies the connector and setting. Pin numbering and outcomes are not universal; use the diagram and table for the exact model.
#1 Best Overall
- Type: Long Handle Open Jumper Cap, Standard 2.54mm, Black 100pcs.
- Overall size: 13.5 x 5 x 2.4mm /0.53" x 0.2" x 0.1" (LxWxH).
- Rated Current: 30AMP Contact Resistance: 20 milliohm Max Withstand Voltage: 1000VAC/DC Insulation Resistance: 1000MQ Min.
- Operating Temperature: -40 to +105 centigrade, Contact Material: Brass Contact Plating, Insulator Material: Polyester (UL94V-0).
- Jumper caps for hard drives, circuit boards, computer interface cards, motherboards to control internal devices, etc.
Some manuals identify pin 1 with a square solder pad. Supermicro uses that marking in its X14SBHM documentation, but check the markings and instructions on your own board rather than assuming every manufacturer uses the same indicator.
What jumper caps are used for
Manufacturing or service modes
Some boards use a jumper to select a special operating state. In Supermicro’s documented example, pins 1–2 are the normal setting and pins 2–3 select manufacturing mode. This assignment applies to that board, not to three-pin headers generally.
Rank #2
- Type: Jumper Caps, Fit for 2.54mm Pitch Pin Header
- Size: 6x5x2.5mm / 0.23x0.2x0.1 inch
- Quantity: 200pcs Black Jumper Caps
- Function: These are used for controlling the settings of your internal devices motherboards. Optimize your system configurations with high quality standard jumper caps.
- Use: Standard 2.54mm jumper caps for use on Hard Drives, Circuit Board, Computer Interface cards, etc. These are also for use with Arduino, RaspberryPI and propeller prototype boards.
Clearing CMOS
DFI’s CS181 manual documents a CMOS-clear header with pins 1–2 as normal and pins 2–3 as clear CMOS. For that specific board, the manual says to power off and unplug the system, move the cap to pins 2–3 for a few seconds, then return it to pins 1–2 before reconnecting power. Do not use those pin numbers or that timing for another model; follow its own manual.
Some devices need no adjustment
A jumper block’s presence does not mean it should be changed. Seagate says its SATA drives require no jumper-block adjustments in its Serial ATA basics guidance. Check the documentation for the exact drive or device instead of applying procedures from older or different hardware.
Rank #3
- ♛【Package Includes】: This kit has a full assortment of circuit board jumper caps. Sizes includes: 2.5 x 3 x 1.27mm/0.1 x 0.12 x 0.05’’, 4 x 3.6 x 2.0mm/0.16 x 0.14 x 0.08’’, 5 x 6.5 x 2.54mm/0.2 x 0.25 x 0.1’’, 5 x 13.5 x 2.54mm/0.2 x 0.53 x 0.1’’. Variety of sizes, black, red, blue, yellow, white, green circuit board jumper caps are sold together, total for 300pcs. Comes in a clear storage box. Plenty of quantity for your daily use and replacement.
- ♛【Premium Material】: These mixed jumper caps kits are made of high quality metal and plastic materials. Smooth surface, hard and strong, durable, not easy to rust, not easy to fade or deform. They are lightweight and portable, non-magnetic and non-toxic, no burden to use.
- ♛【Product Type】: There are two main types of the most common motherboard jumpers. One is only 2 pins and the other is a jumper cap. The open and closed design allows for quick and easy connections and disconnections for increased efficiency.
- ♛【Powerful Function】: Short circuit caps are manual switches on the motherboard. The motherboard circuit can be changed by connecting different jumper PINs through the jumper cap. Used to control internal device motherboard settings. Optimise your system configuration with high quality standard jumper caps.
- ♛【Wide Application】: Shunts short circuit connection pin blocks are universally applicable to Arduino, Raspberry PI boards, circuit boards, motherboards, computer interfaces, electrical engineering, and ETC. Suitable for PCB PC DVD HDD motherboards short circuits, and hard disc drives.
How to handle a jumper safely
- Find the exact model’s documentation. Locate the jumper label, pin diagram, function table, default position, and any warnings. Do not move a block whose function is undocumented or marked reserved.
- Identify pin 1 and the intended pair. Use the board’s own marking and manual. Confirm which pins the cap must bridge and what the selected state does.
- Follow the stated power precautions. Lenovo instructs users working on the SR950 V3 to turn off the server and disconnect all power cords and external cables before moving jumpers. Apply the instructions for your specific device; do not assume it is safe to reposition a jumper while powered.
- Move the cap only as directed. If it is hard to grip, Schneider Electric’s Rack iPC instructions say needle-nose pliers may help. That is guidance for that product family, not a universal requirement.
- Restore the documented normal position when required. Some procedures, such as DFI’s CS181 CMOS-clear example, require returning the cap to its normal pair before power is restored. Check whether your device’s procedure has the same requirement.
Choosing a replacement cap
If a cap is missing, verify that a replacement physically fits the target header and is appropriate for the device. The cited manuals do not establish a universal cap size, pin spacing, or cross-device compatibility. Do not bridge pins with improvised conductive material or install a cap based only on appearance.
Quick Recap
Best Value
- These are two pin jumpers without handle (also called shunts) that will create an electrical connection for the 2.0 mm (0.0787 inch) male Pin headers. Commonly used to modify settings on a board or device;
- Mother board jumper is a manual switch on the motherboard, Through the jumper cap connected to different jumpers PIN, You can change the motherboard circuit;
- The most common motherboard jumpers are mainly two, One is only two needles, The other part is jumper cap;
- Jumper cap, Which is an active part, The outer layer is insulated plastic, The inner conductive material can be inserted in the jumper pin above the two jumper pin connected;
- 200 pieces black standard computer jumper caps without handle, PP plastic box packaging.
Rank #4
- Type:Circuit Board Jumper Caps,Suitable for 2.54mm Pitch Pin Header.
- Dimension: 6x5x2.5mm / 0.23x0.2x0.1".Optimize your system configuration with a high quality standard jumper cap.
- Function: Used for controlling the settings of your internal devices motherboards.
- Purpose: Standard 2.54mm jumper caps for use on Hard Drives, Circuit Board, Computer Interface cards, etc.Also used for Arduino, Raspberry PI and propeller prototype boards.
- Package included: 200x Black Jumper Caps.
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