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Two Raspberry Pi HATs can physically fit together and still conflict electrically. To determine whether a specific pair can be stacked, compare each board’s documented GPIO connections, reserved functions, HAT+ class, power requirements, and mechanical clearance. A shared or ambiguously documented pin means the result should be treated as a conflict or left unverified—not assumed safe.
What the HAT+ stacking rule does—and does not—allow
The Raspberry Pi HAT+ specification permits one HAT+ from each class on a host at a time: one Standard HAT+ or legacy HAT, one Stackable HAT+, and one Power HAT+. This is a class-count rule, not a guarantee that every combination of boards is compatible.
A Stackable HAT+ is defined by its electrical connections: it uses only the ID pins and does not electrically connect to GPIOs 2–27. Boards outside that definition cannot be presumed stackable just because their connectors line up. Even a class-compliant arrangement must be able to power its peripherals. The specification also says Stackable HAT+s are not backwards-compatible with older firmware, so check the firmware requirements for the particular board.
Boards without an EEPROM—including PoE and PoE+ HATs—are outside the HAT+ standard. The specification says they may or may not combine with other HAT+s; consult the documentation for the exact board rather than inferring compatibility from the standard.
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- Package quantity: you will receive 8 pieces extra tall female o.1 inch pitch stacking header, enough quantity to meet your different needs, for replacement or as backup
- Compatible with: these stacking headers are compatible with Raspberry Pi A+ Pi Model B+ Pi 2 Pi 3 Pi 4C
- Dimension: the pin spacing is approx. 2.54 mm/ 0.1 inch, the pin length is approx. 12 mm/ 0.47 inch, the pin thickness is approx. 0.6 mm/ 0.02 inch; Please check the size carefully before orderingC
- Quality material: extra tall header features gold color plated; Insulation material - PA6T, high temperature resistant; Contact resistance is max 20 mΩ, nominal current is 3 AC
- Widely applications: these extra stacking headers can be widely applied for PCB circuit boards in electronics, electrical appliances, and meters so on
How a compatibility checker should evaluate two HATs
A useful checker needs evidence about the exact board models and revisions being considered. It should compare both boards across several independent dimensions rather than returning a simple yes based on the connector or product label.
| Check | What to compare | Why it matters |
|---|---|---|
| GPIO connections and functions | GPIO numbers, electrical connections, and documented alternate functions, including I2C, SPI, and serial buses. | Boards connected to the same pin may interfere electrically, even if their software configuration differs. |
| Reserved and special-purpose pins | ID, reset, and other reserved pins; distinguish documented active use from pins explicitly marked unused. | A pin’s role may be important even when it is not a general-purpose input or output. |
| HAT+ class and metadata | Each board’s stated class, EEPROM presence, and any device-tree overlay information. | Class rules and boot configuration help explain intended behavior, but do not prove that all hardware combinations work. |
| Power | Supply requirements and the load of the boards’ peripherals. | A pin-compatible stack can still exceed what its power arrangement can provide. |
| Physical fit | Board dimensions, clearance, connector orientation, and whether a stacking header is present. | Electrical compatibility does not ensure the boards can be assembled without obstruction. |
| Evidence quality | Official pin map or specification, vendor documentation, or an unverified community report. | The checker should make uncertainty visible when documentation is missing or ambiguous. |
Its result should name the conflicting pin and function, identify the documentation used, and distinguish an established collision from an unknown. A broad claim that “these HATs stack” is not reliable unless it applies to the specific models and revisions.
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- Elevated HAT Design: Lifts your Pi HAT over any Pi accessories like cooler or heat sink, creating critical clearance over on-board components
- Universal Compatibility: Comes with two heights of GPIO and PoE network extender stacking headers, matching with 11mm and 16mm M2.5 hex standoffs, compatible with Raspberry Pi 5 4B 3B+
- Adjustable Height Configuration: Easy to move the plastic spacer of the headers for height adjustment, turn the body height to 8.5mm, 11mm, 13.5mm, 16mm. And 7mm screws are long enough to mount them up
- Technical Specifications: 2.54mm header body height 11mm with pin length 8.5mm, body height 16mm with pin length 3.5mm. M2.5 standoffs available in 11mm and 16mm lengths. M2.5 Philips head screws measure 7mm
- Complete Package Contents: 1x 2x20 header 8.5mm pin, 1x 2x20 header 3.5mm pin, 1x 2x2 header 8.5mm pin, 1x 2x2 header 3.5mm pin, 4x M2.5x11 standoffs, 4x M2.5x16 standoffs, 16x M2.5 screws
Why EEPROM detection is not a compatibility guarantee
At boot, Raspberry Pi firmware probes the ID_SD and ID_SC pins for a HAT EEPROM. The EEPROM can identify the board and name a device-tree overlay, which provides pin configuration and driver information. That metadata helps the system configure supported hardware; it does not certify that another board can share the same pins or that the pair is mechanically and electrically compatible.
Example: reading the Build HAT pin information
Raspberry Pi’s Build HAT documentation lists GPIO0 and GPIO1 for its ID PROM, GPIO4 for reset, GPIO14 and GPIO15 for Tx/Rx, and GPIO16 and GPIO17 for RTS/CTS, marked unused. A checker should preserve those distinctions: a pin documented as unused is not the same as a pin documented as actively used, while ID and reset functions deserve explicit attention in a comparison.
Rank #3
- The 40pin header kit box is a full range of 40pin component boxes for electronic enthusiasts DIY.
- Packing List: 2 * 2x20 Long Female Header (Pin Len: 12mm), 2 * 2x20 Long Female Header (Pin Len: 11mm), 2 * 2x20 in-line female row (Pin Len: 5.5mm), 2 * 2x20 straight Pin Header, 2 * 2x20 90 Degree Curved Pin Header, 2 * 2x20 90 Degree Curved Pin Header,1 * GPIO Edge Extension
- Application: It can be used for Raspberry Pi pin expansion, and it can also be used for all 40pin pins. Occasion, such as Tinker board, jetson nano and other standard 40Pin equipment pin extensions, etc.
- Stacking header for Raspberry Pi 4, Pi 3, Pi 2, Pi Model B+, Pi A+, Pi Zero, Pi Zero W, Pi Zero 2, Pi Zero W2
For a proposed second board, compare its documented electrical connections and configured functions against those assignments. If its documentation does not provide enough detail to determine whether a connection conflicts, the checker should say that compatibility is unverified rather than turn missing information into a pass.
Does a stacking header solve a pin conflict?
No. A long GPIO extension or stacking header can leave pins accessible above a HAT, which helps with physical access and assembly. Raspberry Pi’s AI HAT+ product page lists a 16 mm stacking header among the included hardware. The header does not isolate, reassign, or otherwise resolve a shared-pin conflict; the pin maps still need to be checked.
Rank #4
- Extra Tall Design Clears Ports: this header elevates your add-on board (HAT) sufficiently to clear the bulky USB and Ethernet ports on modern Pis
- Secure Stacking for Multi-Layer Projects - Enables you to reliably stack and connect multiple HATs, sensor breakouts, or custom PCBs onto your Pi
- 2x20 pins, 2.54mm pitch, dimension 8.5/5.0/4.5mm
- Pack of 2
A practical decision for a proposed stack
- Identify the exact boards. Record the model and revision of each HAT; do not generalize from another board in the product family.
- Find the board documentation. Use its pin map or specification to list electrical connections, alternate functions, reserved pins, and any pins marked unused.
- Compare overlaps. Check whether both boards connect to the same GPIO or rely on the same bus or function. Treat documented electrical overlap as a conflict unless the board documentation explicitly establishes a compatible arrangement.
- Check class and firmware. Apply the HAT+ class limit only where the boards meet the specification, and verify firmware requirements for a Stackable HAT+.
- Check power and physical fit separately. Confirm the supply can support the peripherals, then check clearances, connector orientation, and header arrangement.
- Report the confidence level. State which sources support the conclusion. If a pin map or relevant compatibility detail is absent or ambiguous, mark the result unverified.
There is no established published statistic for how often Raspberry Pi HATs conflict over pins. Compatibility must be assessed from the documentation for the boards in question; a stacking label, EEPROM, or extension header alone is not enough to establish a safe combination.
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Quick Recap
Best Value
- Packing List: 2 pcs 2x20 Female Header (Pin Len: 12mm), 2 pcs 2x20 Female Header (Pin Len: 10.7mm), 2 pcs 2x20 Female Header (Pin Len: 5.5mm), 2 pcs 2x20 Pin Header, 2 pcs 1x20 Pin Header
- The 2x20 Pin Header is for Raspberry Pi Zero / Zero W/ Zero 2 W use
- Material: Insulated plastic, hard metal pin
- Application: Widely be used in Raspberry Pi DIY projects, such as for electronic circuit, PCB circuit board, electronic project etc
- Stacking header for Raspberry Pi 5, Raspberry Pi 4, Pi 3, Pi 2, Pi Model B+, Pi A+, Pi Zero, Pi Zero W
Product prices and availability are accurate as of the date/time indicated and are subject to change. Any price and availability information displayed on Amazon at the time of purchase will apply.
