To tell whether two Raspberry Pi HATs can be stacked, compare their documented GPIO connections and functions, then check HAT+ class, power, software configuration and physical fit. The HAT+ specification allows one board from each of its three classes—Standard, Stackable and Power—but that rule is not a blanket guarantee that any pair of boards is electrically or mechanically compatible. A reliable compatibility agent should name the exact boards and revisions it checked, explain any pin conflicts and say when the documentation is insufficient to decide.
What does “stackable” mean under the HAT+ specification?
Raspberry Pi’s HAT+ specification says, “You can connect one HAT+ from each class to a host Raspberry Pi at a time.” The classes are Standard, Stackable and Power. In particular, a Stackable HAT+ must use only the ID pins and must not electrically connect to GPIOs 2–27. The class rule permits one board from each class, including one Standard HAT+ or legacy HAT, but does not establish that every combination will work. The setup still has to meet its power needs, and physical clearance and board-specific connections still matter. See the HAT+ specification.
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The specification also notes that Stackable HAT+s are not backwards-compatible with older firmware. Check the firmware requirements for the particular board rather than assuming the class label alone settles compatibility.
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It should compare evidence for the exact models and revisions, not infer compatibility from a product name or from the fact that both boards fit a 40-pin header. For each board, the useful evidence is a vendor pin map or equivalent documentation showing electrical connections, functions and any pins explicitly marked unused.
#1 Best Overall
- 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
- Identify the exact boards and revisions. A result for one revision should not be generalized to another unless its documentation confirms the same connections.
- Compare GPIO use and alternate functions. Look for overlap in GPIO numbers and connections to I2C, SPI, serial or other buses. Distinguish a pin physically connected by board circuitry from a pin merely assigned or configured by software.
- Account for special pins. Include identification, reset and reserved functions in the comparison. Treat a pin documented as unused differently from one with an active connection.
- Check class, EEPROM and software requirements. Class membership and overlay support add useful context, but neither replaces the electrical comparison.
- Check power and physical assembly. Confirm that the Raspberry Pi supply can support the boards and their peripherals, and that board dimensions, header orientation, clearance and any stacking header allow the proposed assembly.
- Explain the evidence and confidence. Cite the applicable board documentation and identify unresolved questions. If a pin map is missing or ambiguous, report the combination as unverified rather than declaring it safe.
What can a HAT EEPROM tell you—and what can’t it prove?
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; the overlay supplies pin-configuration and driver information. That metadata helps the system configure supported hardware, but it is not proof that two boards have compatible electrical connections, enough power or adequate physical clearance. A successful identification or overlay load should not be treated as a compatibility test.
Why does a board-level pin map matter?
The Raspberry Pi Build HAT documentation illustrates the detail an agent should preserve. It lists GPIO0 and GPIO1 for the ID PROM, GPIO4 for reset, GPIO14 and GPIO15 for Tx/Rx, and GPIO16 and GPIO17 for RTS/CTS, which are marked unused. A useful comparison reports both the function and status as documented: it should not turn a listed-but-unused pin into an active conflict, nor overlook a reset or identification connection. See the Build HAT documentation.
Rank #2
- 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
Which HATs need extra caution?
Not every GPIO add-on follows the HAT+ standard. The specification specifically identifies boards without an EEPROM, including PoE and PoE+ HATs, as outside that standard. Such boards may or may not work alongside other HAT+s; their own documentation is the relevant guide. An agent should not assign them a HAT+ class or infer compatibility from the class-count rule.
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Does a stacking header resolve a pin conflict?
No. A long GPIO extension header can make pins accessible above a fitted HAT, which may help with physical assembly, but it does not change which pins either board electrically uses. Raspberry Pi’s AI HAT+ product page lists a 16 mm stacking header among the included hardware; that is a mechanical feature, not evidence that another board’s pin use will be compatible. Consider clearance and header orientation separately from the pin 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
How should an agent report its verdict?
A useful answer is specific and evidence-based, not just “compatible” or “incompatible.” It should name the board models and revisions, list overlapping GPIOs and their documented functions, note reserved or unused pins, and identify the source of each claim. It should separately describe class and firmware considerations, power requirements and physical fit. Where a vendor pin map is absent or unclear, the right verdict is that compatibility cannot be verified from the available documentation—not a confident yes.
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
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
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