Change WiFi Connection on ESP32 Without Re-uploading Code

If you’ve ever built an IoT project with an ESP32, you know the pain of changing your home Wi-Fi or hotspot SSID: every time you switch networks, you have to open Arduino IDE, edit the code, and re-upload it.
That process is slow and frustrating—especially when your ESP32 is already mounted inside a project enclosure.

This tutorial fixes that forever. You’ll learn how to create a dynamic Wi-Fi configuration portal and web dashboard so that users can connect the ESP32 to any network—without re-flashing the firmware.

By the end of this guide, you’ll have:

A smart Wi-Fi Manager built on ESP32
A Captive Portal that appears automatically (just like public Wi-Fi)
A Web Dashboard to view and modify saved SSID/password
EEPROM-based storage so credentials persist after power cycles
Zero dependence on Arduino IDE after deployment 🚀

🧠 How It Works

Startup check:
When the ESP32 powers up, it looks for stored SSID/password in EEPROM or flash memory.
If valid credentials found:
It auto-connects to that network and prints the IP address.
If no credentials or connection fails:
It launches a Wi-Fi Access Point (AP) mode, hosting a small web server.
User connects to that AP (e.g., ESP32_Setup) and opens 192.168.4.1.
The page lets you type a new SSID and password.
ESP32 saves the data locally, reboots, and connects to the new Wi-Fi—without re-uploading code.
You can also revisit the dashboard anytime to change credentials manually.

⚙️ Hardware & Software Requirements

Hardware:

ESP32 Dev Module
Micro-USB Cable
Breadboard (optional)
Power Supply (5 V 2 A recommended)

Software:

Arduino IDE (2.2 or later)
ESP32 Board Package
Libraries:
- WiFi.h
- WebServer.h
- EEPROM.h

🧩 Circuit Connections

This project doesn’t require external components, but if you want to test visual feedback, connect:

An LED to GPIO 2 (with 220 Ω resistor) → shows Wi-Fi status
Optional push-button to GPIO 0 → factory-reset credentials

ESP32 GPIO2  → LED → 220Ω → GND
ESP32 GPIO0  → Push Button → GND

That’s all you need for the hardware setup.

💻 Arduino IDE Setup

Install the ESP32 board package from the Board Manager.
Choose your board: Tools > Board > ESP32 Dev Module.
Set upload speed to 921600 and Flash size to 4 MB.
Select your COM port.

🔧 Code Structure Overview

Before writing the full sketch, let’s understand the structure:

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

#define LED_PIN 2

WebServer server(80);

String ssid, password;

void setup() {
  Serial.begin(115200);
  EEPROM.begin(512);
  pinMode(LED_PIN, OUTPUT);

  // Load stored credentials
  ssid = readString(0);
  password = readString(50);

  if (connectWiFi()) {
    Serial.println("Connected to WiFi!");
  } else {
    startAPMode();
  }
}

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

This skeleton shows three major functions you’ll implement later:

connectWiFi() → tries saved SSID/password
startAPMode() → starts captive portal
readString() / writeString() → EEPROM helpers

🧠 EEPROM Memory Concept

The ESP32’s flash can emulate EEPROM. We’ll store:

SSID (0–49 bytes)
Password (50–99 bytes)

EEPROM ensures that even if the ESP32 reboots or loses power, credentials remain safe.

🌐 User Experience Preview

Here’s how your final setup will behave:

Step	Action	What Happens
1	Power on ESP32	Tries to connect using saved Wi-Fi
2	If fail	Creates AP “ESP32_Setup”
3	User connects & opens `192.168.4.1`	Sees web form
4	User enters SSID + Password	ESP32 saves and reboots
5	ESP32 connects to new Wi-Fi	Displays IP on Serial Monitor
6	Dashboard available at new IP	View/change Wi-Fi any time

🧭 Next Up

In Part 2, we’ll write the complete code for the Wi-Fi Manager Portal, including:

HTML form for credentials
WebServer handling
EEPROM storage and retrieval
Automatic connection logic

Now that you understand the concept, let’s dive into the complete working code that lets your ESP32 switch Wi-Fi networks anytime — without re-uploading the sketch.

This part covers:
✅ Captive Portal setup
✅ Web form for Wi-Fi credentials
✅ EEPROM storage
✅ Auto reconnect and reboot sequence

💻 Complete Arduino Code

Copy and paste this code into your Arduino IDE 👇

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

#define EEPROM_SIZE 200
#define LED_PIN 2

WebServer server(80);

String ssid;
String password;

// --------- Function to Read String from EEPROM ----------
String readStringFromEEPROM(int startAddr) {
  String data = "";
  char c;
  for (int i = startAddr; i < startAddr + 50; i++) {
    c = EEPROM.read(i);
    if (c == '\0') break;
    data += c;
  }
  return data;
}

// --------- Function to Write String to EEPROM ----------
void writeStringToEEPROM(int startAddr, String data) {
  for (int i = 0; i < 50; i++) {
    if (i < data.length()) EEPROM.write(startAddr + i, data[i]);
    else EEPROM.write(startAddr + i, '\0');
  }
  EEPROM.commit();
}

// --------- WiFi Connection Function ----------
bool connectWiFi() {
  if (ssid == "" || password == "") return false;

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

  int retry = 0;
  while (WiFi.status() != WL_CONNECTED && retry < 20) {
    delay(500);
    Serial.print(".");
    retry++;
  }
  Serial.println();

  if (WiFi.status() == WL_CONNECTED) {
    Serial.println("✅ Connected to WiFi!");
    Serial.print("IP Address: ");
    Serial.println(WiFi.localIP());
    digitalWrite(LED_PIN, HIGH);
    return true;
  } else {
    Serial.println("❌ Connection Failed!");
    return false;
  }
}

// --------- Captive Portal Web Form ----------
void handleRoot() {
  String html = "<html><head><title>ESP32 WiFi Manager</title></head><body>";
  html += "<h2>WiFi Configuration Portal</h2>";
  html += "<form action='/save' method='POST'>";
  html += "SSID:<br><input type='text' name='ssid'><br>";
  html += "Password:<br><input type='password' name='pass'><br><br>";
  html += "<input type='submit' value='Save'>";
  html += "</form></body></html>";
  server.send(200, "text/html", html);
}

// --------- Save Credentials ----------
void handleSave() {
  String newSSID = server.arg("ssid");
  String newPass = server.arg("pass");

  if (newSSID.length() > 0 && newPass.length() > 0) {
    writeStringToEEPROM(0, newSSID);
    writeStringToEEPROM(50, newPass);
    server.send(200, "text/html", "<h3>✅ Saved! Rebooting...</h3>");
    delay(2000);
    ESP.restart();
  } else {
    server.send(200, "text/html", "<h3>❌ Invalid Input! Try Again.</h3>");
  }
}

// --------- Start AP Mode for WiFi Config ----------
void startAPMode() {
  Serial.println("🔄 Starting Access Point...");
  WiFi.mode(WIFI_AP);
  WiFi.softAP("ESP32_Setup", "12345678");

  IPAddress IP = WiFi.softAPIP();
  Serial.print("AP IP address: ");
  Serial.println(IP);

  server.on("/", handleRoot);
  server.on("/save", handleSave);
  server.begin();

  digitalWrite(LED_PIN, LOW);
  Serial.println("🌐 Web Portal Ready. Connect to 'ESP32_Setup' and open 192.168.4.1");
}

// --------- Setup ----------
void setup() {
  Serial.begin(115200);
  pinMode(LED_PIN, OUTPUT);
  EEPROM.begin(EEPROM_SIZE);

  ssid = readStringFromEEPROM(0);
  password = readStringFromEEPROM(50);

  Serial.println("Stored SSID: " + ssid);
  Serial.println("Stored Password: " + password);

  if (!connectWiFi()) {
    startAPMode();
  }
}

// --------- Loop ----------
void loop() {
  server.handleClient();
}

🔍 Code Explanation

Let’s break down the main parts of this sketch:

🧠 EEPROM Functions

We use two functions:

readStringFromEEPROM() → retrieves SSID and password from memory.
writeStringToEEPROM() → saves new credentials permanently.

EEPROM is initialized with EEPROM.begin(200) to allocate 200 bytes.

🌐 WebServer & Captive Portal

We use the WebServer library to host a small HTML page.

When the user connects to ESP32_Setup, they can open 192.168.4.1 and see a simple Wi-Fi setup page.
Once they hit Save, credentials are stored and the ESP restarts.

🔁 Smart Boot Logic

On startup:

If saved SSID/password exist → try connecting.
If connection fails → create a new Access Point (ESP32_Setup).

This ensures your ESP32 never gets stuck offline.

💡 LED Indicator

You can connect an LED to GPIO 2:

ON = Connected to Wi-Fi
OFF = Access Point mode

It’s optional but helpful for debugging.

📶 How the Captive Portal Works

When the ESP32 fails to connect to Wi-Fi, it automatically enters AP mode:

Creates a local network ESP32_Setup
Assigns itself an IP 192.168.4.1
Hosts the configuration page

You can connect your mobile or laptop to that Wi-Fi and open the portal.

Now that your ESP32 can save and switch Wi-Fi credentials dynamically, it’s time to add a Web Dashboard to manage, monitor, and reset the connection directly from a browser.

In this part, you’ll learn how to:
✅ Build a modern dashboard to show Wi-Fi details
✅ Add Reset/Erase buttons for saved credentials
✅ Display current connection strength (RSSI)
✅ Host the dashboard directly from ESP32’s flash memory

💻 Dashboard Overview

Your dashboard will include:

Wi-Fi Network Name
Signal Strength
Connection Status (Connected / Disconnected)
Local IP Address
“Change Wi-Fi” Button to launch Captive Portal again
“Erase Credentials” Button to delete stored SSID and password

When accessed through a browser, it will look something like this 👇

--------------------------------------------
🌐 ESP32 WiFi Manager Dashboard
--------------------------------------------
📡 Network: My_Home_WiFi
📶 Signal: -45 dBm
✅ Status: Connected
💻 IP: 192.168.0.112
[Change Wi-Fi] [Erase Credentials]
--------------------------------------------

🧠 Adding the Dashboard Page in Code

We’ll extend our previous sketch and add new routes for:

/dashboard → main page showing Wi-Fi info
/reset → to clear saved credentials

Here’s the updated code section 👇

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

#define EEPROM_SIZE 200
#define LED_PIN 2

WebServer server(80);
String ssid, password;

// Function Declarations
String readStringFromEEPROM(int startAddr);
void writeStringToEEPROM(int startAddr, String data);
bool connectWiFi();
void startAPMode();

// ----------- NEW FUNCTION: Erase Credentials -----------
void eraseCredentials() {
  for (int i = 0; i < 100; i++) EEPROM.write(i, '\0');
  EEPROM.commit();
  server.send(200, "text/html", "<h3>🧹 Credentials Erased! Rebooting...</h3>");
  delay(2000);
  ESP.restart();
}

// ----------- NEW FUNCTION: Show Dashboard -----------
void handleDashboard() {
  String html = "<html><head><title>ESP32 WiFi Dashboard</title>";
  html += "<style>body{font-family:Arial;text-align:center;background:#101010;color:#00FF99;}</style></head><body>";
  html += "<h2>🌐 ESP32 Wi-Fi Manager Dashboard</h2>";
  
  if (WiFi.status() == WL_CONNECTED) {
    html += "<p><b>Network:</b> " + WiFi.SSID() + "</p>";
    html += "<p><b>IP Address:</b> " + WiFi.localIP().toString() + "</p>";
    html += "<p><b>Signal Strength:</b> " + String(WiFi.RSSI()) + " dBm</p>";
    html += "<p><b>Status:</b> ✅ Connected</p>";
  } else {
    html += "<p><b>Status:</b> ❌ Disconnected</p>";
  }

  html += "<br><button onclick=\"location.href='/'\">Change Wi-Fi</button>";
  html += "<button onclick=\"location.href='/reset'\">Erase Credentials</button>";
  html += "</body></html>";

  server.send(200, "text/html", html);
}

// ----------- Handle Root Page (WiFi Setup) -----------
void handleRoot() {
  String html = "<html><head><title>WiFi Setup</title></head><body>";
  html += "<h2>ESP32 WiFi Setup</h2>";
  html += "<form action='/save' method='POST'>";
  html += "SSID:<br><input type='text' name='ssid'><br>";
  html += "Password:<br><input type='password' name='pass'><br><br>";
  html += "<input type='submit' value='Save Wi-Fi'>";
  html += "</form>";
  html += "<br><a href='/dashboard'>Go to Dashboard</a>";
  html += "</body></html>";
  server.send(200, "text/html", html);
}

// ----------- Update AP Mode -----------
void startAPMode() {
  WiFi.mode(WIFI_AP);
  WiFi.softAP("ESP32_Setup", "12345678");
  IPAddress IP = WiFi.softAPIP();
  Serial.print("Access Point started at: ");
  Serial.println(IP);

  server.on("/", handleRoot);
  server.on("/save", handleSave);
  server.on("/dashboard", handleDashboard);
  server.on("/reset", eraseCredentials);
  server.begin();

  Serial.println("🌐 Configuration Portal is active!");
}

💡 What’s New in This Part

🖥️ 1. Dashboard Page

The /dashboard route displays real-time network data (SSID, RSSI, IP).
It uses WiFi.RSSI() to show signal strength.

🧹 2. Erase Credentials

/reset clears all stored SSID and password values in EEPROM.
After reboot, ESP32 starts in Access Point mode again — ready for new Wi-Fi credentials.

🔄 3. Navigation Links

The dashboard links back to the setup page, so users can easily switch between pages without code re-uploading.

📲 How to Test the Dashboard

Upload the full code to your ESP32.
Connect to your configured Wi-Fi or to the ESP32_Setup access point.
Open your browser and enter the device IP (e.g. 192.168.4.1 or assigned IP).
You’ll see the dashboard interface with connection details.
Try clicking:
- Change Wi-Fi: Opens setup form.
- Erase Credentials: Clears memory and reboots ESP32.

✅ Result: A fully functional Web Dashboard + Wi-Fi Manager inside your ESP32!

🧠 Next Up

In Part 4, we’ll:

Discuss real-world use cases
Add OTA updates for firmware upgrades
Share troubleshooting tips
Explore advanced automation use

🌍 1. Real-World Applications

This dynamic Wi-Fi Manager system isn’t just a cool experiment — it’s used in many commercial and professional IoT devices. Here are some examples:

🏠 Smart Home Devices

You can integrate this code into:

Smart plugs or lights
Smart switches and fans
IoT-enabled sensors (temperature, water level, etc.)
When a user installs your device, they simply connect to the ESP32 setup network and configure Wi-Fi — just like setting up a smart bulb!

🏢 Industrial IoT Systems

Industries often move devices between different Wi-Fi networks.
This system allows technicians to update network credentials without using a laptop or programming cable — saving massive setup time.

🚜 Remote Agricultural Monitoring

For ESP32-based soil sensors, weather stations, or irrigation controllers — being able to change Wi-Fi remotely helps when relocating devices or updating access points.

🚀 DIY & Learning Projects

Students and developers can integrate this same logic into their prototypes — giving them professional-grade configuration capability like real IoT appliances.

⚙️ 2. Adding OTA (Over-the-Air) Updates

You can expand your project to allow firmware updates over Wi-Fi without connecting ESP32 to a PC.

Here’s a quick snippet to enable OTA:

#include <WiFi.h>
#include <WebServer.h>
#include <EEPROM.h>
#include <ESPmDNS.h>
#include <WiFiClient.h>
#include <WiFiUdp.h>
#include <ArduinoOTA.h>

void setup() {
  Serial.begin(115200);
  EEPROM.begin(200);
  pinMode(2, OUTPUT);

  // Connect to stored WiFi
  ssid = readStringFromEEPROM(0);
  password = readStringFromEEPROM(50);
  WiFi.begin(ssid.c_str(), password.c_str());

  // OTA Setup
  ArduinoOTA.onStart([]() { Serial.println("Start updating..."); });
  ArduinoOTA.onEnd([]() { Serial.println("\nUpdate Complete!"); });
  ArduinoOTA.begin();
}

void loop() {
  ArduinoOTA.handle();  // Keep OTA listening
}

✅ With this feature, you can upload new firmware via Wi-Fi, directly from the Arduino IDE or your web dashboard — no USB cable needed!

📡 3. Improving Security

While this project is easy to use, real IoT applications should have:

Password protection for setup and dashboard pages
HTTPS/TLS encryption (possible via ESP32 SSL libraries)
Token-based authentication with Firebase or MQTT brokers
Hidden AP credentials to prevent unauthorized access

Adding a login page to your portal (using HTML + JavaScript) is highly recommended for production devices.

💾 4. Expanding Storage (Preferences Library)

Instead of EEPROM, you can use the Preferences library — a modern alternative that allows saving data as key-value pairs, and offers more stability.

Example:

#include <Preferences.h>
Preferences preferences;

preferences.begin("wifi", false);
preferences.putString("ssid", "MyWiFi");
preferences.putString("pass", "12345678");
preferences.end();

This is safer for long-term projects, as EEPROM has limited write cycles.

🧠 5. Troubleshooting Common Issues

Let’s go over a few common problems and how to fix them:

Issue	Possible Cause	Solution
ESP32 not connecting to Wi-Fi	Incorrect SSID or password	Double-check your credentials and case sensitivity
Web portal not loading	Wrong IP address	Try `192.168.4.1` or check the Serial Monitor
Wi-Fi not reconnecting after power loss	EEPROM not initialized correctly	Ensure `EEPROM.begin(200)` is called in setup
Captive portal doesn’t appear	DNS not redirecting	Open browser manually and enter `192.168.4.1`
Device reboots repeatedly	Memory overflow or bad save	Clear EEPROM using `/reset` route

💡 Tip: Always test using your mobile hotspot before deploying in routers with firewalls or MAC filters.

🧩 6. Future Upgrades

Once you’re comfortable with the basics, you can expand this project into a complete IoT configuration suite. Here are a few upgrade ideas:

🔗 A. Firebase Integration

Add Firebase database code so that your ESP32 automatically uploads Wi-Fi status and sensor data to the cloud.

📱 B. Mobile-Friendly Dashboard

Design a responsive HTML page using Bootstrap or TailwindCSS for a better mobile experience.

🔔 C. Real-Time Monitoring

Include sensor data (like temperature, humidity, or relay status) in your web dashboard — updating in real time using AJAX.

⚡ D. Multi-Device Configuration

Store multiple Wi-Fi networks in memory and let ESP32 automatically switch between them if one fails.

🧭 E. MQTT Compatibility

Use MQTT for fast, lightweight data transfer between your ESP32 and a cloud broker (like HiveMQ or Adafruit IO).

🎯 7. Key Highlights Recap

Feature	Description
Wi-Fi Manager	Change network anytime without re-uploading code
Web Dashboard	Manage connections and view signal status
EEPROM Storage	Saves credentials permanently
Captive Portal	Easy setup via mobile or laptop
OTA Update	Upload new code wirelessly
Reset Function	Erase stored data anytime

🏁 8. Final Thoughts

With this project, you’ve turned your ESP32 into a professional-grade IoT device that’s flexible, portable, and user-friendly.
No more hardcoding SSIDs, no more manual reprogramming — just connect, configure, and control.

This setup is the foundation of every real-world IoT product, whether it’s:

A smart home automation system,
A remote weather station,
Or an industrial monitoring unit.

You’ve built something that’s not only educational but deployable.

So go ahead — integrate it into your next IoT project, add your own dashboard styling, and make your ESP32 truly smart!

🎥 Full Tutorial: Watch the complete working video and demo on YaranaIoT Guru YouTube Channel for live setup, troubleshooting, and dashboard walkthroughs.

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