Change WiFi on ESP32 Without Re-uploading Code

Welcome to YaranaIoT Guru’s advanced ESP32 tutorial! In this project, we’ll teach you how to change Wi-Fi credentials on ESP32 without re-uploading code.

Many IoT projects require Wi-Fi credentials to be updated frequently. Traditionally, you need to modify the code and re-upload it, which is inconvenient for deployed devices. In this guide, we’ll implement a web dashboard and captive portal setup, allowing users to:

Change Wi-Fi SSID & password directly from a browser
Avoid knowing the ESP32 IP address
Automatically connect to the new network

This method is perfect for home automation, IoT devices, and portable ESP32 projects.

🔹 Why This Approach is Useful

Eliminates the need to reprogram devices every time Wi-Fi changes
Supports dynamic networks in homes, offices, and labs
Provides a professional user interface for Wi-Fi configuration
Works with multiple IoT devices in distributed setups

🔹 Project Goals

Configure ESP32 as Access Point (AP) if it cannot connect to Wi-Fi
Host a captive portal web page for Wi-Fi credentials
Store credentials in non-volatile memory (EEPROM / Preferences)
Connect to the new Wi-Fi automatically
Provide optional dashboard for multiple device control

🔹 Applications

IoT devices that need frequent Wi-Fi updates
Home automation appliances with dynamic network environments
Smart sensors, smart plugs, or security devices
Classroom or office IoT deployments

🔹 Required Components

Component	Quantity	Description
ESP32 Dev Board	1	Microcontroller with Wi-Fi
USB Cable	1	Power and programming
Breadboard & Jumper Wires	Optional	For LEDs or relays if included
PC or Mobile Device	1	Access portal via browser
Arduino IDE	1	Development environment

🔹 Step 1: Circuit Overview

This project is primarily software-driven. Optional LEDs or relays can be connected for demonstration:

LED → GPIO2
Relay → GPIO5
Connect 220Ω resistor with LED to GND

The focus is on Wi-Fi configuration, so hardware requirements are minimal.

🔹 How This Works (High-Level)

ESP32 starts and attempts to connect to saved Wi-Fi credentials
If unsuccessful, it starts an Access Point (AP)
User connects to the AP via phone or PC → automatic captive portal opens
User enters new Wi-Fi credentials → ESP32 saves them in non-volatile memory
ESP32 connects to the new network without needing IP or code re-upload

🔹 Step 1: Required Libraries

To implement this project, you need the following Arduino libraries:

WiFi.h → for Wi-Fi connectivity
ESPAsyncWebServer.h → to host the web server
AsyncTCP.h → dependency for ESPAsyncWebServer
Preferences.h → for storing Wi-Fi credentials in non-volatile memory

Installation:

Go to Sketch → Include Library → Manage Libraries
Search for ESPAsyncWebServer and install
Search for AsyncTCP and install

🔹 Step 2: Setup Preferences Storage

ESP32’s Preferences library allows storing Wi-Fi credentials permanently:

#include <Preferences.h>
Preferences preferences;

void setup() {
  preferences.begin("wifiCreds", false); // Namespace
  String ssid = preferences.getString("ssid", "");
  String password = preferences.getString("pass", "");
}

If credentials exist → ESP32 tries to connect
If not → ESP32 starts Access Point mode

🔹 Step 3: Configuring the Captive Portal

Core logic:

Start AP mode if Wi-Fi connection fails
ESP32 hosts a web page for SSID and password
User submits credentials → ESP32 saves in Preferences and restarts

Code Example:

#include <WiFi.h>
#include <ESPAsyncWebServer.h>
#include <Preferences.h>

Preferences preferences;
AsyncWebServer server(80);

String ssid = "";
String password = "";

void setup() {
  Serial.begin(115200);
  preferences.begin("wifiCreds", false);
  
  ssid = preferences.getString("ssid", "");
  password = preferences.getString("pass", "");
  
  WiFi.mode(WIFI_STA);
  if (ssid != "" && password != "" && WiFi.begin(ssid.c_str(), password.c_str()) == WL_CONNECTED) {
    Serial.println("Connected to saved WiFi!");
  } else {
    startAPMode();
  }
}

void startAPMode() {
  WiFi.mode(WIFI_AP);
  WiFi.softAP("ESP32_Config_Portal");
  Serial.println("Access Point Started: ESP32_Config_Portal");

  server.on("/", HTTP_GET, [](AsyncWebServerRequest *request){
    request->send(200, "text/html", 
      "<form action=\"/save\" method=\"POST\">"
      "SSID:<input type='text' name='ssid'><br>"
      "Password:<input type='password' name='pass'><br>"
      "<input type='submit' value='Save'>"
      "</form>");
  });

  server.on("/save", HTTP_POST, [](AsyncWebServerRequest *request){
    ssid = request->getParam("ssid", true)->value();
    password = request->getParam("pass", true)->value();
    
    preferences.putString("ssid", ssid);
    preferences.putString("pass", password);

    request->send(200, "text/html", "<h2>WiFi Saved! Restarting...</h2>");
    delay(2000);
    ESP.restart();
  });

  server.begin();
}

✅ Now, when the ESP32 cannot connect to saved Wi-Fi:

It creates ESP32_Config_Portal AP
User connects → captive portal opens automatically
Enter new credentials → ESP32 saves and connects

🔹 Step 4: Testing the Captive Portal

Upload the code to ESP32
Disconnect ESP32 from Wi-Fi or use new credentials
Check available Wi-Fi networks → connect to ESP32_Config_Portal
Browser automatically opens → enter SSID & password
ESP32 stores them and connects to the new network

🔹 Step 5: Optional Enhancements

Add LED indicator: blink while in AP mode
Add multiple device support with unique AP names
Validate SSID & password input for better UX

🔹 1. Dynamic Web Dashboard

Instead of a simple HTML form, we can create a full-featured dashboard:

Displays current Wi-Fi status
Allows changing SSID and password
Shows LED status or sensor readings (optional)

HTML Example for ESP32 Web Server:

server.on("/", HTTP_GET, [](AsyncWebServerRequest *request){
  String html = "<html><head><title>ESP32 WiFi Manager</title></head><body>";
  html += "<h1>ESP32 WiFi Configuration</h1>";
  html += "<p>Current SSID: " + WiFi.SSID() + "</p>";
  html += "<form action='/save' method='POST'>";
  html += "SSID:<input type='text' name='ssid'><br>";
  html += "Password:<input type='password' name='pass'><br>";
  html += "<input type='submit' value='Save'>";
  html += "</form></body></html>";
  
  request->send(200, "text/html", html);
});

✅ Users now see current Wi-Fi SSID and can update credentials seamlessly.

🔹 2. Managing Multiple Devices

If you have multiple ESP32 devices, each can:

Start its own AP with unique name, e.g., ESP32_Device1, ESP32_Device2
Host the same dashboard interface for credentials
Users can connect and configure each device individually

Code for Unique AP Names:

String apName = "ESP32_Device_" + String((uint32_t)ESP.getEfuseMac(), HEX);
WiFi.softAP(apName.c_str());
Serial.println("AP Started: " + apName);

🔹 3. Switching Wi-Fi Without IP

Traditional web servers require knowing ESP32’s IP. With captive portal, it’s automatic:

Device broadcasts AP if it cannot connect to Wi-Fi
User connects → browser automatically opens the portal
No need to enter IP addresses
Credentials are saved → ESP32 reconnects automatically

This is ideal for IoT devices deployed in remote locations.

🔹 4. Adding Optional Features

LED / Relay Control on Dashboard
- Extend dashboard to toggle GPIO pins: <p><a href='/LED1=ON'><button>LED ON</button></a> <a href='/LED1=OFF'><button>LED OFF</button></a></p>
- ESP32 updates device status in real-time
Sensor Readings
- Add temperature, humidity, or motion sensor data to the dashboard
- Users can monitor environment and update settings in real-time
Network Diagnostics
- Display signal strength (RSSI)
- Show connection status, uptime, and last updated time

🔹 5. Testing & Troubleshooting

Disconnect ESP32 from your Wi-Fi to trigger AP mode
Connect multiple devices and ensure unique AP names
Test dashboard on mobile and desktop browsers
Verify saved credentials are applied after ESP32 restarts

🔹 1. Cloud Integration

Integrating your ESP32 with a cloud platform like Firebase, Blynk, or Ubidots allows:

Remote monitoring of connected Wi-Fi networks
Ability to push updates or change configurations remotely
Collect device logs for maintenance and analytics

Example: Firebase Integration

#include <HTTPClient.h>
#include <WiFi.h>

void sendWiFiStatusToCloud(String ssid) {
  if(WiFi.status() == WL_CONNECTED){
    HTTPClient http;
    String url = "https://your-project.firebaseio.com/device_status.json";
    String payload = "{\"SSID\":\"" + ssid + "\"}";
    http.begin(url);
    http.addHeader("Content-Type", "application/json");
    http.POST(payload);
    http.end();
  }
}

✅ Every time ESP32 connects to Wi-Fi, the SSID is sent to Firebase, allowing cloud tracking.

🔹 2. Over-The-Air (OTA) Updates

OTA allows you to update firmware remotely without USB:

Include the ArduinoOTA library:

#include <ArduinoOTA.h>

Add OTA setup in setup():

ArduinoOTA.begin();

In loop(), call:

ArduinoOTA.handle();

Upload new firmware via Arduino IDE over Wi-Fi
Eliminates the need to physically access the device

🔹 3. Security Measures

Password Protection on Web Portal

if(request->getParam("password")->value() != "YourSecret") {
  request->send(403, "text/plain", "Forbidden");
  return;
}

Use HTTPS / SSL Certificates for cloud communication
Wi-Fi Credentials Encryption
- Store encrypted SSID & password in Preferences
- Prevents unauthorized access if EEPROM is read

🔹 4. Optional Advanced Features

Device Grouping
- Assign multiple ESP32 devices to groups for bulk configuration
Sensor Data Dashboard
- Display temperature, humidity, motion, or LED status
Custom Captive Portal Themes
- Brand with your own logos and styling

🔹 5. Future Upgrades

Integrate voice assistants (Alexa, Google Assistant) to switch networks via commands
Add MQTT protocol for real-time cloud IoT communication
Implement automatic Wi-Fi failover for multiple networks
Extend dashboard to control multiple devices, LEDs, or relays

🔹 6. Final Testing & Deployment

Disconnect ESP32 → triggers captive portal
Connect via mobile → enter new credentials
Verify automatic Wi-Fi reconnection
Test dashboard, cloud sync, OTA update, and security measures
Ensure all devices maintain connectivity and report real-time status

🔹 Conclusion

With this guide, you have learned how to:

Build an ESP32 captive portal to update Wi-Fi dynamically
Store credentials in non-volatile memory
Create a web dashboard for device management
Integrate cloud tracking and OTA updates
Implement security and advanced IoT features

“This project transforms your ESP32 into a self-configuring, secure, and cloud-ready IoT device — no IP, no re-upload, just seamless Wi-Fi management.”
— YaranaIoT Guru

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