Published April 10, 2026

Flash ESP32/ESP8266 OTA Using Your Smartphone

Update ESP32/ESP8266 code wirelessly via WiFi. Upload once via USB, then use a browser to send new code—no cables needed, even in hard spots

IntermediateFull instructions provided1 hour10

Flash ESP32/ESP8266 OTA Using Your Smartphone

Things used in this project

Hardware components

Espressif ESP32

NodeMCU ESP8266 Breakout Board

USB Cable, USB Type C Plug

Android device

Software apps and online services

Arduino IDE

Story

Introduction

This project shows you how to update the code on your ESP32 or ESP8266 microcontroller without plugging in a USB cable. Normally, every time you want to change your program, you need to physically connect the board to your laptop. With this method, you upload a special sketch to the board once via USB, and after that, all future code updates happen wirelessly over WiFi. Just open your phone's browser, go to the board's IP address, pick your new code file, and hit upload. That's it. Super useful when your board is mounted somewhere hard to reach.

Details

To update firmware on any microcontroller over the air, the board needs a way to receive new code wirelessly and write it to flash memory. The ESP32 and ESP8266 already have built-in WiFi, which makes them perfect candidates. The Web Updater OTA method works by running a tiny web server on the board itself. You open the board's IP address in your smartphone browser, upload a compiled.bin file, and the board flashes itself and reboots. No USB cable needed after the first setup.

The ESP32 manages OTA using a dual-partition system in its flash memory — ota_0 and ota_1. New firmware is written to the inactive partition while the board keeps running. Once the write is verified, the board switches over and reboots into the new code. This is what makes OTA safe. If the update fails, the board rolls back to the previous working firmware automatically.

Step 1 — Initial USB upload (one time only)

The board's factory image has no OTA capability, so the first upload must be done via USB from the Arduino IDE. Arduino IDE already includes a ready-to-use example. Navigate to File > Examples > ArduinoOTA > OTAWebUpdater, enter your WiFi credentials, and upload.

Step 2 — Find the board's IP address

After uploading, open Serial Monitor at 115200 baud and press the EN/Reset button. The board will print its assigned IP address, for example 192.168.1.47. Note it down, or better yet, assign it a static IP from your router's DHCP settings so it never changes. This is the address you will type into your phone's browser every time you want to push an update.

Step 3 — Export new sketches as.bin files

For every future update, write your sketch on the PC as normal, then go to Sketch > Export Compiled Binary. This saves a.bin file in your sketch folder. Transfer it to your phone via Google Drive, WhatsApp, AirDrop, or email, whatever is convenient. Make sure the file lands somewhere your phone's browser file picker can access it.

Step 4 — Flash from your smartphone browser

Open Chrome or Safari on your phone and go to http://192.168.1.47 You will see the OTA login and upload page served by the board. Log in with the credentials set in your sketch, select your.bin file, and tap Upload. The process takes 10 to 30 seconds. The board reboots automatically and runs the new firmware.

For a much cleaner upload interface with a progress bar, consider using the ElegantOTA library instead of the default OTAWebUpdater example. It requires only three extra lines of code added to any existing sketch and produces a polished browser UI.

The only rule to remember: every sketch you upload from now on must include the OTA routine. If you upload a sketch without it, the web server disappears and you will have to go back to USB for the next update. Download all sketch files and Gerber PCB files from the links above. PCBs can be ordered from JLCPCB starting at just $2 for 5 boards, check them out here: https://jlcpcb.com

ESP32 / ESP8266 OTA Web Updater (Basic)

#include <WiFi.h>
#include <WebServer.h>
#include <ElegantOTA.h>

const char* ssid = "YOUR_WIFI_SSID";
const char* password = "YOUR_WIFI_PASSWORD";

WebServer server(80);

void setup() {
  Serial.begin(115200);

  WiFi.begin(ssid, password);
  Serial.println("Connecting to WiFi...");

  while (WiFi.status() != WL_CONNECTED) {
    delay(1000);
    Serial.print(".");
  }

  Serial.println("\nConnected!");
  Serial.print("IP Address: ");
  Serial.println(WiFi.localIP());

  server.on("/", []() {
    server.send(200, "text/plain", "ESP OTA Ready");
  });

  ElegantOTA.begin(&server);  // Start ElegantOTA

  server.begin();
}

void loop() {
  server.handleClient();
}

Credits

Daniel D'Souza

2 projects • 0 followers

Embedded systems & robotics engineer with 9+ yrs in IoT & hardware, building practical projects and hands-on STEM learning

Flash ESP32/ESP8266 OTA Using Your Smartphone

Things used in this project

Hardware components

Software apps and online services

Story

Introduction

Details

Step 1 — Initial USB upload (one time only)

Step 2 — Find the board's IP address

Step 3 — Export new sketches as.bin files

Step 4 — Flash from your smartphone browser

Code

ESP32 / ESP8266 OTA Web Updater (Basic)

Credits

Daniel D'Souza

Comments

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Flash ESP32/ESP8266 OTA Using Your Smartphone

Flash ESP32/ESP8266 OTA Using Your Smartphone

Things used in this project

Hardware components

Software apps and online services

Story

Introduction

Details

Step 1 — Initial USB upload (one time only)

Step 2 — Find the board's IP address

Step 3 — Export new sketches as.bin files

Step 4 — Flash from your smartphone browser

Code

ESP32 / ESP8266 OTA Web Updater (Basic)

Credits

Daniel D'Souza

Comments

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