Two ESP32 dev boards with the same silkscreen number can expose GPIO in completely different orders, and burning a whole afternoon chasing a “why is my sensor reading zero” bug usually comes down to a strapping pin or an input-only GPIO nobody flagged. A pocket pinout reference on Android is the fastest way to catch that before the soldering iron heats up. The apps below cover pin numbering, strapping and boot behaviour, ADC and touch maps, PWM channels, and the practical caveats that never make it onto the board’s paper card.
We gave preference to apps that work fully offline, respect a $2 one-time payment over subscriptions, and keep a database wide enough to cover DevKitC v4, LOLIN S3, TinyPICO, and the growing ESP32-C3 and -S3 families. A couple of programming tools are on the list too, because moving from “read the pinout” to “flash a test sketch” is a one-tap step when the toolchain is on the same phone.
What to look for in an ESP32 pinout app
- Board-specific views, not just the SoC datasheet. A DevKitC exposes different pins than an S3 DevKit.
- Flag the traps. Input-only pins, boot straps, JTAG defaults, and pins wired to onboard flash need to be called out, not hidden in fine print.
- Peripheral map. ADC channels, DAC, touch, PWM, RTC, and SPI defaults matter more than the raw numbering.
- Offline database. Solder in the field, on planes, and in labs with no signal.
- A serial or MQTT companion. So once the wiring is right, testing it does not require a laptop.
Quick comparison
| App | Best for | Free plan | Starting price/mo | Rating |
|---|---|---|---|---|
| PinOut | Board-specific ESP32 and Arduino diagrams | Yes | Free | 4.5 |
| Electrodoc Pro | Full electronics toolkit + pinouts | Free trial | One-time paid | 4.5 |
| ElectroDroid | Widely used reference with plugins | Yes | Pro one-time | 4.7 |
| Arduino IDE | Compile and flash sketches from phone | Yes | Free | 4.1 |
| Termux | Python and esptool.py from Android | Yes | Free | 4.5 |
| SerialWiFiTerminal | On-the-go serial monitor over USB or Wi-Fi | Yes | Free | 4.3 |
| IoT MQTT Panel | Sanity-check a wired ESP32 over MQTT | Yes | Free | 4.6 |
| Wokwi | Simulate the wiring before soldering | Yes | Pro from $7/mo | 4.6 |
The apps
1. PinOut — Best board-specific reference for ESP32 and Arduino
PinOut is the app we open first whenever a new board lands on the bench. It carries board-specific diagrams for the DevKitC, LOLIN, TinyPICO, Wemos S2 Mini, and dozens of Arduino form factors, and each pin is annotated with its GPIO number, alternate function, and any strapping or input-only warnings. Diagrams work offline once downloaded.
Where it falls short: Newer C6 and H2 boards can lag a firmware release or two behind. Search is fine but not fuzzy.
Pricing:
- Free: All board diagrams, offline access.
- Paid: None.
Platforms: Android.
Bottom line: The strongest “just tell me which pin does what on this board” app on Android.
2. Electrodoc Pro — Best all-round electronics toolkit
Electrodoc Pro is the Swiss Army knife. Pinouts sit alongside resistor colour codes, LED calculators, PCB trace-width helpers, and a serial console. The ESP32 pinout section is not as deep as PinOut’s, but the surrounding calculators pay off the moment you also need to pick a series resistor or verify a voltage divider.
Where it falls short: UI density is high, so it takes a couple of sessions to learn which section holds which tool.
Pricing:
- Free: Basic reference tools.
- Paid: One-time purchase unlocks the full Pro toolset.
Platforms: Android, iOS.
Bottom line: Pick this if you want one app that covers the whole electronics bench, not just pinouts.
3. ElectroDroid — Best long-standing reference with plugins
ElectroDroid is the elder statesman of Android electronics reference apps. Pinouts for ESP32 boards, common ICs, and every connector you might ever plug into a Raspberry Pi hat live inside one browser-style menu. A plugin ecosystem adds specialised references (transistor types, antenna calculators) without bloating the base install.
Where it falls short: The interface still looks like a 2015 Android app. Some plugin packs are paid one-time add-ons.
Pricing:
- Free: Core reference and pinouts.
- Paid: Pro version and plugin bundles.
Platforms: Android.
Bottom line: A staple. Install it alongside PinOut, not instead of it.
4. Arduino IDE — Best mobile compile and flash
Arduino IDE on Android is the official cloud-backed editor. Write a test sketch, pick your ESP32 board target, and flash over USB-OTG or Wi-Fi. It is the fastest path from “which GPIO is this?” to “the LED is blinking on GPIO 2, so my wiring works.”
Where it falls short: Requires an Arduino Cloud account for library sync. Complex builds still deserve a laptop.
Pricing:
- Free: Editor, cloud sketches, board flashing.
- Paid: Optional Arduino Cloud plans for more device connections.
Platforms: Android, iOS, web.
Bottom line: Great sanity-check tool the moment you have a datasheet pin in hand and want to test it.
5. Termux — Best for esptool.py from the phone
Termux is a full Linux terminal on Android. Install Python, pip install esptool, and you can flash firmware to an ESP32 over USB-OTG without a laptop nearby. It also runs Ampy, mpremote, and rshell for MicroPython workflows.
Where it falls short: Requires the F-Droid build for full package support since the Play Store version is frozen. Setup is technical if you have never used a Linux shell.
Pricing:
- Free: Everything.
- Paid: None.
Platforms: Android.
Bottom line: The way to keep a full ESP32 toolchain in your pocket. Learning curve, but pays off fast.
6. SerialWiFiTerminal — Best mobile serial monitor
SerialWiFiTerminal exposes a proper serial console over USB-OTG or over Wi-Fi to any ESP32 running a small telnet-style stub. Handy for debugging boot logs when the phone is the only screen nearby, and it saves session logs to plain text for later.
Where it falls short: Fussy about USB-OTG chipsets on some Android phones. Older builds sometimes need to be paired manually.
Pricing:
- Free: All features.
- Paid: None.
Platforms: Android.
Bottom line: The mobile alternative to a bench serial monitor. Good for field work.
7. IoT MQTT Panel — Best for testing wiring over MQTT
IoT MQTT Panel turns any Android phone into a dashboard for an ESP32 running MQTT. Build a panel of switches, sliders, and gauges, subscribe to topics, and confirm your wiring is doing what the sketch says. It is the fastest way to remove wiring uncertainty from a bug: if the sensor value shows up in the panel, the pin choice is fine, and the bug is in code.
Where it falls short: Requires an MQTT broker somewhere on the network. Nothing wrong with running Mosquitto on a Raspberry Pi for this.
Pricing:
- Free: All features.
- Paid: None.
Platforms: Android.
Bottom line: The go-to panel for confirming a wiring choice with real data.
8. Wokwi — Best pre-solder simulator
Wokwi is a browser-based ESP32 simulator that runs surprisingly well on Android in Chrome or a WebView shell. Wire a board in the drag-and-drop editor, load a sketch, and watch the exact GPIO you were planning to use light up an LED or spit sensor data. Useful for teaching, prototyping, and confirming a pin choice before touching the iron.
Where it falls short: Not a native Android app, so touch targets can be small on phones. Advanced peripherals need the Pro tier.
Pricing:
- Free: Public projects and most boards.
- Paid: Pro plans from around $7/mo for private projects and premium peripherals.
Platforms: Web (works on Android via browser), desktop.
Download: Open in browser
Bottom line: The one to reach for before soldering, especially when the sensor is expensive or fragile.
How to pick the right one
- If you only need one pinout reference: PinOut.
- If you want an all-round electronics toolkit: Electrodoc Pro.
- If you already trust ElectroDroid: keep it, and add PinOut for board-specific views.
- If you want to flash sketches from the phone: Arduino IDE for beginners, Termux for anyone comfortable with a shell.
- If you need to debug boot messages in the field: SerialWiFiTerminal.
- If you want to prove the wiring works with real data: IoT MQTT Panel.
- If you want to test the design before touching a board: Wokwi.
FAQ
What is the best free ESP32 pinout app for Android?
PinOut. It has the widest board-specific coverage and works fully offline once diagrams are downloaded.
Why does GPIO 12 or GPIO 15 sometimes prevent boot on my ESP32?
Those are strapping pins. If a strapping pin is held high or low at power-on, the chip enters an alternate boot mode. Check the app diagrams under “boot” or “strapping” annotations before wiring them to sensors.
Can I flash an ESP32 without a computer?
Yes. Use USB-OTG plus Arduino IDE for Android, or Termux with esptool.py. Both approaches work over a USB-C to USB-A adapter and a data-capable cable.
Are these pinout apps accurate for the ESP32-S3 and ESP32-C3?
PinOut and Electrodoc cover most S3 and C3 boards, but check the app’s board list before buying a brand-new variant. Some C6 and H2 boards are still catching up in the reference apps.
Do any of the apps show ADC noise or PWM channel maps?
Electrodoc Pro and ElectroDroid both list ADC channels and PWM assignments. For noise characteristics, cross-reference the app diagram with Espressif’s official datasheet.
Which app plays best offline?
PinOut and ElectroDroid both work fully offline. Wokwi requires a browser and network. Arduino IDE needs the account only for cloud sync, not for local flashing.
