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HATs (Hardware Attached on Top) extend a Raspberry Pi’s capability well beyond its base GPIO pins — these are the ones that solve genuinely common project needs rather than being novelty add-ons.
| Best For | Pick | Why | |
|---|---|---|---|
| A PoE HAT for power-and-data-in-one installs | waveshare Power Over Ethernet (PoE) HAT for Raspberry Pi 4B/3B+, 802.3af/at PoE Network Standard, 5V USB-A&12V Header Outputs, PoE HAT Onboard Cooling Fan and MP8676 Buck Chip, Isolated | Based on Raspberry Pi 40pin GPIO interface, suitable for Raspberry Pi 3B+/4B | View → |
| An RTC HAT for accurate offline timekeeping | Adafruit Ultimate GPS HAT for Raspberry Pi A+/B+/Pi 2 [ADA2324] | Dimensions of the item packaging: L 15.0 x W 9.8 x H 1.0 cm | View → |
| A relay HAT for controlling real-world hardware | WatangTech 4-CH Relay HAT for Raspberry Pi Single Board Computers | 4 Independent Channels: Control multiple devices separately with 4 onboard relays (250V/5A per channel) | View → |
A PoE HAT for power-and-data-in-one installs
A Power over Ethernet HAT eliminates the need for a separate power cable entirely, a real convenience for a Pi mounted somewhere a power outlet is inconvenient to reach.
- Based on Raspberry Pi 40pin GPIO interface, suitable for Raspberry Pi 3B+/4B
- Support PoE power over Ethernet, support IEEE 802.3af/at PoE network standard
- Using a fully isolated switch mode power supply (SMPS)
An RTC HAT for accurate offline timekeeping
A real-time clock HAT keeps accurate time even without internet access to sync from, important for any offline or air-gapped project that logs timestamped data.
![Adafruit Ultimate GPS HAT for Raspberry Pi A+/B+/Pi 2 [ADA2324]](https://m.media-amazon.com/images/I/41kA8zmNXxL._SL500_.jpg)
- Dimensions of the item packaging: L 15.0 x W 9.8 x H 1.0 cm
- Item packaging weight: 0.022046001186074866 pounds
- Number of packs1
A relay HAT for controlling real-world hardware
A relay HAT lets a Pi safely switch higher-voltage devices — sprinklers, lights, small appliances — directly from GPIO commands, a common building block for home automation projects.
- 4 Independent Channels: Control multiple devices separately with 4 onboard relays (250V/5A per channel)
- High-Current Design: Supports motors, lights, and appliances up to 250V/5A per relay
- Dual Protection: Optocoupler isolation combined with jumper-selectable pins for anti-interference and flexibility
Confirm HAT compatibility with your specific Pi model before buying — the 40-pin header has stayed consistent, but some HATs have physical clearance issues with certain case designs.
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