ESP32 Pin Quick Reference
Pick your chip and see which GPIOs are safe to use, which to avoid, and which can read analog voltages.
| GPIO | Badges | Notes |
|---|
What the badges mean
✅ general use ⚠️ strapping pin 🔒 flash/PSRAM ⬇️ input-only 📈 ADC1 📉 ADC2 ⓘ use with care (USB, UART, JTAG, crystal… see notes)
Not every pin is the same. Strapping pins are read at power-up to decide how the chip boots, so things you connect there can stop your board from starting. Input-only pins can read but not drive an LED. ADC pins can measure voltages; on chips with two ADCs, ADC2 is shared with Wi-Fi, so use ADC1 if Wi-Fi is on. When unsure, use the “good first pins”.
Your board may use some pins (USB, LEDs, buttons, flash). Check its pinout. Modules don’t break out every chip pin either. This tool covers chips, not specific boards.
Learn more: Your first ESP32… · Read a temperature sensor with ESP32 · Control a 5V relay module safely · Forum: ESP32 & MCUs (“3.3 V vs 5 V”, “Reading a sensor”) · LED resistor calculator · Resistor colour code
Found an error? Report it in the forum. ADC2/Wi-Fi: ESP-IDF ADC oneshot driver (“ADC2 is also used by Wi-Fi”).