Build Your ESP32 Temperature & Humidity Web Server with a DHT Sensor🌡️

Want to monitor temperature and humidity using your ESP32? Today, we’re going to transform our ESP32 microcontroller into a real-time temperature and humidity monitoring station that serves data through a web interface.

Before We Begin: If you’re completely new to the ESP32, I recommend checking out my previous blog post, an Ultimate ESP32 Beginner’s Guide. We’ve covered the basics of setting up your development environment, installing board support, and uploading your first program.

What You’ll Need?

Hardware Components

ESP32 Development Board (any variant: ESP32 DevKit, NodeMCU-32S, etc.)
DHT11 or DHT22 Temperature/Humidity Sensor
Breadboard (optional but recommended)
Jumper Wires (male-to-female or male-to-male)
Micro-USB Cable for programming and power
10kΩ Resistor (only if using DHT11 without built-in pull-up)

🚀 I highly recommend getting a complete ESP32 starter kit.
It will save you time, money, and frustration—and help you learn IoT much faster.

Software Requirements

Arduino IDE
ESP32 Board Support Package
DHT Sensor Library by Adafruit

Note: If you haven’t set up your Arduino IDE with ESP32 support yet, please follow my previous ESP32 setup guide before proceeding.

🌡️ DHT11 vs DHT22 (Quick Comparison)

Feature	DHT11	DHT22
Temperature Range	0–50°C	-40–80°C
Humidity Range	20–80%	0–100%
Accuracy	Moderate	High
Price	Cheaper	Slightly expensive

Both sensors work similarly in code; just change the DHT type in your sketch.

🔌 Circuit Diagram & Connections

DHT Sensor Pins:

VCC → ESP32 3.3V or 5V
GND → ESP32 GND
DATA → ESP32 GPIO 26 (can be any digital pin)

Important Note:
If you are using a DHT sensor without an internal pull-up resistor, connect a 10kΩ resistor between VCC and DATA. This ensures reliable communication between the sensor and the ESP32.

🧠 ESP32 Web Server Code

Library to Install: DHT sensor library by Adafruit

#include <WiFi.h>
#include <WiFiClient.h>
#include <WebServer.h>
#include <ESPmDNS.h>
#include <DHT.h>

const char *ssid = "YOUR-Network";
const char *password = "YOUR-PASSWORD";

WebServer server(80);
DHT dht(26, DHT11);

void handleRoot() {
  char msg[1500];

  snprintf(msg, 1500,
           "<html>\
  <head>\
    <meta http-equiv='refresh' content='4'/>\
    <meta name='viewport' content='width=device-width, initial-scale=1'>\
    <link rel='stylesheet' href='https://use.fontawesome.com/releases/v5.7.2/css/all.css' integrity='sha384-fnmOCqbTlWIlj8LyTjo7mOUStjsKC4pOpQbqyi7RrhN7udi9RwhKkMHpvLbHG9Sr' crossorigin='anonymous'>\
    <title>ESP32 DHT Server</title>\
    <style>\
    html { font-family: Arial; display: inline-block; margin: 0px auto; text-align: center;}\
    h2 { font-size: 3.0rem; }\
    p { font-size: 3.0rem; }\
    .units { font-size: 1.2rem; }\
    .dht-labels{ font-size: 1.5rem; vertical-align:middle; padding-bottom: 15px;}\
    </style>\
  </head>\
  <body>\
      <h2>ESP32 DHT Server!</h2>\
      <p>\
        <i class='fas fa-thermometer-half' style='color:#ca3517;'></i>\
        <span class='dht-labels'>Temperature</span>\
        <span>%.2f</span>\
        <sup class='units'>&deg;C</sup>\
      </p>\
      <p>\
        <i class='fas fa-tint' style='color:#00add6;'></i>\
        <span class='dht-labels'>Humidity</span>\
        <span>%.2f</span>\
        <sup class='units'>&percnt;</sup>\
      </p>\
  </body>\
</html>",
           readDHTTemperature(), readDHTHumidity()
          );
  server.send(200, "text/html", msg);
}

void setup(void) {

  Serial.begin(115200);
  dht.begin();
  
  WiFi.mode(WIFI_STA);
  WiFi.begin(ssid, password);
  Serial.println("");

  // Wait for connection
  while (WiFi.status() != WL_CONNECTED) {
    delay(500);
    Serial.print(".");
  }

  Serial.println("");
  Serial.print("Connected to ");
  Serial.println(ssid);
  Serial.print("IP address: ");
  Serial.println(WiFi.localIP());

  if (MDNS.begin("esp32")) {
    Serial.println("MDNS responder started");
  }
  server.on("/", handleRoot);

  server.begin();
  Serial.println("HTTP server started");
}

void loop(void) {
  server.handleClient();
  delay(2000);//allow the cpu to switch to other tasks
}


float readDHTTemperature() {
  // Sensor readings may also be up to 2 seconds
  // Read temperature as Celsius (the default)
  float t = dht.readTemperature();
  if (isnan(t)) {    
    Serial.println("Failed to read from DHT sensor!");
    return -1;
  }
  else {
    Serial.println(t);
    return t;
  }
}

float readDHTHumidity() {
  // Sensor readings may also be up to 2 seconds
  float h = dht.readHumidity();
  if (isnan(h)) {
    Serial.println("Failed to read from DHT sensor!");
    return -1;
  }
  else {
    Serial.println(h);
    return h;
  }
}

Configure and Upload Code:

First, replace YOUR_WIFI_SSID and YOUR_WIFI_PASSWORD with your actual WiFi credentials
Select your ESP32 board: Tools → Board → ESP32 Arduino → (your specific board)
Select the correct port: Tools → Port
Click the upload button (right arrow icon)

Testing Your Web Server:

After successful upload, open the Serial Monitor (Tools → Serial Monitor)
Set the baud rate to 115200
You should see the ESP32 connecting to WiFi and displaying an IP address
Copy this IP address and paste it into any web browser on your network
Voilà! You should see your temperature and humidity display

📡 How the Project Works

This project combines the ESP32, DHT sensor, and a web server to display live temperature and humidity readings. Here’s a step-by-step overview:

ESP32 connects to your WiFi network – This allows your device to communicate with other devices on the same network.
The DHT sensor reads temperature & humidity – The sensor collects environmental data in real-time.
ESP32 hosts a local web server – This web server runs on the ESP32, waiting for requests from a browser.
Browser requests data from ESP32 – You open a browser and access the ESP32’s IP address to fetch the data.
Web page displays live sensor readings – The browser shows the current temperature and humidity, updated whenever you refresh the page (or automatically if using JavaScript).

What’s Special About This Project?

Unlike basic ESP32 web servers that require you to remember an IP address (like 192.168.1.100), our system will be accessible at http://esp32.local from any device on your local network. No more searching through router logs or using a serial monitor to find your ESP32’s IP address!

Why Use mDNS in IoT Projects?

No IP Address Hunting: Access your ESP32 by a memorable name

Dynamic IP Friendly: Works even if your router assigns different IPs

Professional Feel: Makes your project feel more polished

Easy Network Integration: Works with most modern operating systems

Zero Configuration: No router settings to change

💡 Tip: Later, you can enhance the page to display charts for a smoother experience.

🧠 Code Explanation (More Detailed):

This code turns your ESP32 into a web server that displays live temperature and humidity from a DHT sensor.

1️⃣ Include Libraries

#include <WiFi.h>
#include <WiFiClient.h>
#include <WebServer.h>
#include <ESPmDNS.h>
#include <DHT.h>

WiFi.h / WiFiClient.h → Connects ESP32 to WiFi and handles network communication.
WebServer.h → Creates a local web server on the ESP32.
ESPmDNS.h → Allows you to access the ESP32 using http://esp32.local
DHT.h → Reads data from the DHT sensor (temperature & humidity).

2️⃣ WiFi Credentials

const char *ssid = "Your-Network";
const char *password = "YOUR-PASSWORD";

Replace these with your WiFi name and password. ESP32 uses this to connect to your network.

3️⃣ Server and DHT Initialization

WebServer server(80); // Creates a web server on port 80
DHT dht(26, DHT11);   // DHT sensor connected to GPIO 26, type DHT11

WebServer server(80) → ESP32 will listen for requests on port 80 (default for HTTP).
DHT dht(26, DHT11) → Connects the DHT11 sensor to pin 26.

4️⃣ Handling the Web Page

void handleRoot() {
  char msg[1500];

  snprintf(msg, 1500,
           "<html> ... </html>",
           readDHTTemperature(), readDHTHumidity()
          );
  server.send(200, "text/html", msg);
}

handleRoot() → Function called when someone visits the root URL (/) of your ESP32.
snprintf() → Inserts the live temperature and humidity values into an HTML template.
server.send(200, "text/html", msg) → Sends the HTML page to the browser.

HTML Details:

<meta http-equiv='refresh' content='4'/> → Auto-refresh page every 4 seconds.
<i class='fas fa-thermometer-half'> → Uses Font Awesome icons for a nice visual.
The placeholders %.2f are replaced by temperature and humidity values from the sensor.

5️⃣ Setup Function

void setup(void) {
  Serial.begin(115200);
  dht.begin();
  
  WiFi.mode(WIFI_STA);
  WiFi.begin(ssid, password);

  while (WiFi.status() != WL_CONNECTED) {
    delay(500);
    Serial.print(".");
  }

  Serial.println(WiFi.localIP());

  if (MDNS.begin("esp32")) {
    Serial.println("MDNS responder started");
  }
  server.on("/", handleRoot);

  server.begin();
  Serial.println("HTTP server started");
}

Serial.begin(115200) → Opens the serial monitor for debugging.
dht.begin() → Initializes the DHT sensor.
WiFi.mode(WIFI_STA) → Sets ESP32 as a station to connect to WiFi.
WiFi.begin(ssid, password) → Starts connecting to WiFi.
MDNS.begin("esp32") → Optional: access ESP32 as http://esp32.local.
server.on("/", handleRoot) → Assigns the root URL / to the function handleRoot().
server.begin() → Starts the web server.

6️⃣ Loop Function

void loop(void) {
  server.handleClient();
  delay(2000);
}

server.handleClient() → Checks if a browser has requested the page and responds.
delay(2000) → Tiny pause to allow ESP32 to handle other background tasks.

7️⃣ Reading Sensor Data

Temperature:

float readDHTTemperature() {
  float t = dht.readTemperature();
  if (isnan(t)) {    
    Serial.println("Failed to read from DHT sensor!");
    return -1;
  }
  else {
    Serial.println(t);
    return t;
  }
}

dht.readTemperature() → Reads the temperature in Celsius.
isnan(t) → Checks if the reading failed. Returns -1 if it fails.
Serial.println(t) → Prints the temperature to the serial monitor for debugging.

Humidity:

float readDHTHumidity() {
  float h = dht.readHumidity();
  if (isnan(h)) {
    Serial.println("Failed to read from DHT sensor!");
    return -1;
  }
  else {
    Serial.println(h);
    return h;
  }
}

Works the same way as temperature, but reads humidity.

✅ Conclusion

Congratulations! You’ve successfully built an ESP32 temperature and humidity web server. This project demonstrates the core concepts of IoT: sensor data collection, microcontroller programming, and web server hosting.

The skills you’ve learned here form the foundation for countless other IoT projects. From here, you could expand to monitoring multiple sensors, controlling devices based on conditions, or even creating a complete home automation system.

Remember to experiment with the code, try different sensors, and customize the web interface to match your style. The ESP32 is a remarkably versatile platform, and you’ve just scratched the surface of what it can do!

Build Your ESP32 Temperature & Humidity Web Server with a DHT Sensor🌡️

What You’ll Need?

Hardware Components

Software Requirements

🌡️ DHT11 vs DHT22 (Quick Comparison)

🔌 Circuit Diagram & Connections

🧠 ESP32 Web Server Code

Configure and Upload Code:

Testing Your Web Server:

📡 How the Project Works

What’s Special About This Project?

Why Use mDNS in IoT Projects?

🧠 Code Explanation (More Detailed):

1️⃣ Include Libraries

2️⃣ WiFi Credentials

3️⃣ Server and DHT Initialization

4️⃣ Handling the Web Page

5️⃣ Setup Function

6️⃣ Loop Function

7️⃣ Reading Sensor Data

Temperature:

Humidity:

✅ Conclusion

Resources & Next Steps

Start your journey

About Us

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Categories

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Build Your ESP32 Temperature & Humidity Web Server with a DHT Sensor🌡️

What You’ll Need?

Hardware Components

Software Requirements

🌡️ DHT11 vs DHT22 (Quick Comparison)

🔌 Circuit Diagram & Connections

🧠 ESP32 Web Server Code

Configure and Upload Code:

Testing Your Web Server:

📡 How the Project Works

What’s Special About This Project?

Why Use mDNS in IoT Projects?

🧠 Code Explanation (More Detailed):

1️⃣ Include Libraries

2️⃣ WiFi Credentials

3️⃣ Server and DHT Initialization

4️⃣ Handling the Web Page

5️⃣ Setup Function

6️⃣ Loop Function

7️⃣ Reading Sensor Data

Temperature:

Humidity:

✅ Conclusion

Resources & Next Steps

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