ESP32 - Web Server

In this step-by-step tutorial, we'll show you how to program to make an ESP32 board become a web server. You'll be able to access web pages hosted on the ESP32 using a web browser on your computer or smartphone, enabling you to view data from the ESP32 and control it. To make it easy, we will progress from simple to more challenging steps as follows:

ESP32 relay web browser

Hardware Used In This Tutorial

1×ESP-WROOM-32 Dev Module
1×USB Cable Type-C
1×(Recommended) ESP32 Screw Terminal Adapter

Or you can buy the following sensor kit:

1×DIYables Sensor Kit 30 types, 69 units
Disclosure: some of these links are affiliate links. We may earn a commission on your purchase at no extra cost to you. We appreciate it.

Reading the sensor value from ESP32 via Web

This is relatively simple. The ESP32 code does the following tasks:

  • Creating a web server that listens for HTTP requests from a web browser.
  • Upon receiving a request from a web browser, the ESP32 responds with the following information:
    • HTTP header
    • HTTP body: This includes HTML content and the value read from the sensor.

    Below is the ESP32 code that performs the above tasks:

    /* * This ESP32 code is created by esp32io.com * * This ESP32 code is released in the public domain * * For more detail (instruction and wiring diagram), visit https://esp32io.com/tutorials/esp32-web-server */ #include <WiFi.h> #include <ESPAsyncWebServer.h> const char* ssid = "YOUR_WIFI_SSID"; // CHANGE IT const char* password = "YOUR_WIFI_PASSWORD"; // CHANGE IT AsyncWebServer server(80); void setup() { Serial.begin(9600); // Connect to Wi-Fi WiFi.begin(ssid, password); while (WiFi.status() != WL_CONNECTED) { delay(1000); Serial.println("Connecting to WiFi..."); } Serial.println("Connected to WiFi"); // Print the ESP32's IP address Serial.print("ESP32 Web Server's IP address: "); Serial.println(WiFi.localIP()); // Define a route to serve the HTML page server.on("/", HTTP_GET, [](AsyncWebServerRequest* request) { Serial.println("ESP32 Web Server: New request received:"); // for debugging Serial.println("GET /"); // for debugging request->send(200, "text/html", "<html><body><h1>Hello, ESP32!</h1></body></html>"); }); // Start the server server.begin(); } void loop() { // Your code here }

    Quick Instructions

    • If this is the first time you use ESP32, see how to setup environment for ESP32 on Arduino IDE.
    • Do the wiring as above image.
    • Connect the ESP32 board to your PC via a micro USB cable
    • Open Arduino IDE on your PC.
    • Select the right ESP32 board (e.g. ESP32 Dev Module) and COM port.
    • Open the Library Manager by clicking on the Library Manager icon on the left navigation bar of Arduino IDE.
    • Search “ESPAsyncWebServer”, then find the ESPAsyncWebServer created by lacamera.
    • Click Install button to install ESPAsyncWebServer library.
    ESP32 ESPAsyncWebServer library
    • You will be asked to install the dependency. Click Install All button.
    ESP32 ESPAsyncWebServer dependencies library
    • Copy the above code and open with Arduino IDE
    • Change the wifi information (SSID and password) in the code to yours
    • Click Upload button on Arduino IDE to upload code to ESP32
    • Open the Serial Monitor
    • Check out the result on Serial Monitor.
    COM6
    Send
    Connecting to WiFi... Connected to WiFi ESP32 Web Server's IP address: 192.168.0.2
    Autoscroll Show timestamp
    Clear output
    9600 baud  
    Newline  
    • Take note of the IP address displayed, and enter this address into the address bar of a web browser on your smartphone or PC.
    • As a result, you will see the following output on the Serial Monitor.
    COM6
    Send
    Connecting to WiFi... Connected to WiFi ESP32 Web Server's IP address: 192.168.0.2 ESP32 Web Server: New request received: GET /
    Autoscroll Show timestamp
    Clear output
    9600 baud  
    Newline  
    • Once you access the web browser using the IP address, you will be presented with a very basic web page displaying "Hello, ESP32!". The page will look like the following:
    ESP32 web server

Reading the sensor value from ESP32 via Web

Below is the ESP32 code that prints the temperature value to web page:

/* * This ESP32 code is created by esp32io.com * * This ESP32 code is released in the public domain * * For more detail (instruction and wiring diagram), visit https://esp32io.com/tutorials/esp32-web-server */ #include <WiFi.h> #include <ESPAsyncWebServer.h> const char* ssid = "YOUR_WIFI_SSID"; // CHANGE IT const char* password = "YOUR_WIFI_PASSWORD"; // CHANGE IT AsyncWebServer server(80); float getTemperature() { // YOUR SENSOR IMPLEMENTATION HERE // simulate the temperature value float temp_x100 = random(0, 10000); // a ramdom value from 0 to 10000 return temp_x100 / 100; // return the simulated temperature value from 0 to 100 in float } void setup() { Serial.begin(9600); // Connect to Wi-Fi WiFi.begin(ssid, password); while (WiFi.status() != WL_CONNECTED) { delay(1000); Serial.println("Connecting to WiFi..."); } Serial.println("Connected to WiFi"); // Print the ESP32's IP address Serial.print("ESP32 Web Server's IP address: "); Serial.println(WiFi.localIP()); // Define a route to serve the HTML page server.on("/", HTTP_GET, [](AsyncWebServerRequest* request) { Serial.println("ESP32 Web Server: New request received:"); // for debugging Serial.println("GET /"); // for debugging // get temperature from sensor float temperature = getTemperature(); // Format the temperature with two decimal places String temperatureStr = String(temperature, 2); String html = "<!DOCTYPE HTML>"; html += "<html>"; html += "<head>"; html += "<link rel=\"icon\" href=\"data:,\">"; html += "</head>"; html += "<p>"; html += "Temperature: <span style=\"color: red;\">"; html += temperature; html += "&deg;C</span>"; html += "</p>"; html += "</html>"; request->send(200, "text/html", html); }); // Start the server server.begin(); } void loop() { // Your code here }

Quick Instructions

  • Copy the above code and open with Arduino IDE
  • Change the wifi information (SSID and password) in the code to yours
  • Upload the code to ESP32
  • Once you access the web browser using the IP address, you will be presented with a very basic web page displaying information about the ESP32 board. The page will look like the following:
ESP32 temperature web server

To make the web page look fantastic with a graphic user interface (UI), check out the final section of this tutorial.

※ NOTE THAT:

With the code provided above, to get the termperature update, you have to reload the page on the web browser. In a next part, we will learn how to make web page update the temperature value on backround without reloading the webpage.

Controlling the ESP32 via Web

Controlling something connected to ESP32 is a bit more challenging than just reading a value. That's because ESP32 has to understand the request it receives from the web browser to know what action to take.

For a more comprehensive and detailed example, I recommend checking out the tutorials listed below:

Separating HTML content into another file on Arduino IDE

If you want to create a simple web page with minimal content, you can embed the HTML directly into the ESP32 code, as explained earlier.

However, if you want to make a more sophisticated and impressive web page with larger content, it becomes inconvenient to include all the HTML, CSS, and Javascript directly in the ESP32 code. In this situation, you can use a different approach to manage the code:

  • The ESP32 code will be placed in a .ino file, just like before.
  • The HTML code (HTML, CSS, Javascript) will be placed in a separate .h file. This allows you to keep the web page content separate from the ESP32 code, making it easier to manage and modify.

To do so, we need to do two major steps:

  • Preparing HTML content
  • Programming ESP32

Preparing HTML content

  • Create an HTML file on your local PC that contains the HTML content (HTML, CSS, and Javascript) for your UI design.
  • In the HTML file, where data from ESP32 should be displayed, use an arbitrary value.
  • Test and modify it until you are satisfied.
  • We will put the HTML content in the .h file on the Arduino IDE. See the next step.

Programming ESP32

  • Open the Arduino IDE and create a new sketch. Give it a name, for example, esp32io.com.ino.
  • Copy the code provided below and paste it to the created file.
/* * This ESP32 code is created by esp32io.com * * This ESP32 code is released in the public domain * * For more detail (instruction and wiring diagram), visit https://esp32io.com/tutorials/esp32-web-server */ #include <WiFi.h> #include <ESPAsyncWebServer.h> #include "index.h" // Include the index.h file const char* ssid = "YOUR_WIFI_SSID"; // CHANGE IT const char* password = "YOUR_WIFI_PASSWORD"; // CHANGE IT AsyncWebServer server(80); float getTemperature() { // YOUR SENSOR IMPLEMENTATION HERE // simulate the temperature value float temp_x100 = random(0, 10000); // a ramdom value from 0 to 10000 return temp_x100 / 100; // return the simulated temperature value from 0 to 100 in float } void setup() { Serial.begin(9600); // Connect to Wi-Fi WiFi.begin(ssid, password); while (WiFi.status() != WL_CONNECTED) { delay(1000); Serial.println("Connecting to WiFi..."); } Serial.println("Connected to WiFi"); // Print the ESP32's IP address Serial.print("ESP32 Web Server's IP address: "); Serial.println(WiFi.localIP()); // Serve the HTML page from the file server.on("/", HTTP_GET, [](AsyncWebServerRequest* request) { Serial.println("ESP32 Web Server: New request received:"); // for debugging Serial.println("GET /"); // for debugging request->send(200, "text/html", webpage); }); // Define a route to get the temperature data server.on("/temperature", HTTP_GET, [](AsyncWebServerRequest* request) { Serial.println("ESP32 Web Server: New request received:"); // for debugging Serial.println("GET /temperature"); // for debugging float temperature = getTemperature(); // Format the temperature with two decimal places String temperatureStr = String(temperature, 2); request->send(200, "text/plain", temperatureStr); }); // Start the server server.begin(); } void loop() { // Your code here }
  • Change the WiFi information (SSID and password) in the code to yours
  • Create the index.h file On Arduino IDE by:
Arduino IDE 2 adds file
  • Either click on the button just below the serial monitor icon and choose New Tab, or use Ctrl+Shift+N keys.
  • Give file's name index.h and click OK button
Arduino IDE 2 adds file index.h
  • Copy the below code and paste it to the index.h.
/* * This ESP32 code is created by esp32io.com * * This ESP32 code is released in the public domain * * For more detail (instruction and wiring diagram), visit https://esp32io.com/tutorials/esp32-web-server */ #ifndef WEBPAGE_H #define WEBPAGE_H const char* webpage = R"=====( REPLACE_YOUR_HTML_CONTENT_HERE )====="; #endif
  • Replace the line REPLACE_YOUR_HTML_CONTENT_HERE by your HTML content you prepared before. There is no problem with new line character. The below is an example of index.h file:
/* * This ESP32 code is created by esp32io.com * * This ESP32 code is released in the public domain * * For more detail (instruction and wiring diagram), visit https://esp32io.com/tutorials/esp32-web-server */ #ifndef WEBPAGE_H #define WEBPAGE_H const char* webpage = R"=====( <!DOCTYPE html> <html> <head> <title>ESP32 Temperature</title> </head> <body> <h1>ESP32 Temperature</h1> <p>Temperature: <span style="color: red;"><span id="temperature">Loading...</span> &#8451;</span></p> <script> function fetchTemperature() { fetch("/temperature") .then(response => response.text()) .then(data => { document.getElementById("temperature").textContent = data; }); } fetchTemperature(); setInterval(fetchTemperature, 4000); // Update temperature every 4 seconds </script> </body> </html> )====="; #endif
  • Now you have the code in two files: esp32io.com.ino and index.h
  • Click Upload button on Arduino IDE to upload code to ESP32
  • Access the web page of ESP32 board via web browser as before. You will see it as below:
ESP32 temperature web browser

※ NOTE THAT:

In the above codes:

  • The HTML code is designed to update the temperature in the background at regular intervals, currently set to every 4 seconds in the code. This means that the temperature value is automatically refreshed without the need to manually reload the webpage. You can adjust the update interval in the code to suit your preferences.
  • ESP32 code serves two requests from the web browser.
    • One request to return the HTML content of the webpage
    • The other to return the temperature value requested by the webpage on the backround

For a more comprehensive and detailed illustration, please refer to the ESP32 - DS18B20 Temperature Sensor via Web tutorial

※ NOTE THAT:

  • If you make changes to the HTML content within the index.h file but don't modify anything in the esp32io.com.ino file, the Arduino IDE won't refresh or update the HTML content when you compile and upload the code to the ESP32.
  • To force the Arduino IDE to update the HTML content in this situation, you need to make a modification in the esp32io.com.ino file. For example, you can add an empty line or insert a comment. This action triggers the IDE to recognize that there have been changes in the project, ensuring that your updated HTML content gets included in the upload.

ESP32 Web Server - Multiple Pages

Check out this ESP32 - Web Server Multiple Pages tutorial.

※ OUR MESSAGES