# Arduino project: light the built-in LED using your browser > Learn how to control the Arduino built-in LED from your browser, extending a WiFiNINA web server to turn the LED on or off by visiting the /on and /off URLs. Author: [Flavio Copes](https://flaviocopes.com/about/) | Published: 2021-04-02 | Topics: [Arduino](https://flaviocopes.com/tags/electronics/) | Canonical: https://flaviocopes.com/arduino-project-led-browser/ In this tutorial I want to expand the [Arduino Web Server example](https://flaviocopes.com/arduino-webserver/) to allow us to send commands to the Arduino via the browser. Let's do this: we light up the built-in LED on the Arduino by reaching out to the `/on` URL, and we turn it off by opening the `/off` URL. Anything else does nothing. This is the code from the other tutorial: ```c #include #include WiFiServer server(80); void setup() { char ssid[] = SECRET_SSID; char pass[] = SECRET_PASS; Serial.begin(9600); while (!Serial); int status = WL_IDLE_STATUS; while (status != WL_CONNECTED) { Serial.print("Connecting to "); Serial.println(ssid); status = WiFi.begin(ssid, pass); delay(5000); } Serial.print("IP address: "); Serial.println(WiFi.localIP()); server.begin(); } void loop() { WiFiClient client = server.available(); if (client) { String line = ""; while (client.connected()) { if (client.available()) { char c = client.read(); Serial.write(c); if (c != '\n' && c != '\r') { line += c; } if (c == '\n') { if (line.length() == 0) { client.println("HTTP/1.1 200 OK"); client.println("Content-Type: text/html"); client.println("Connection: close"); // the connection will be closed after completion of the response client.println(); client.println(""); client.println(""); client.println("test"); client.println(""); break; } else { line = ""; } } } } client.stop(); } } ``` In the last `else` you see, we have a full line, so we can check its content before clearing it. In this case we can check for `GET /on ` and `GET /off `, and detect the command we're asked to perform: ```cpp String command = ""; /* ... */ if (line.startsWith("GET /on ")){ command = "on"; } if (line.startsWith("GET /off ")) { command = "off"; } ``` When we are ready to send the response back, we can check the command and turn the LED on or off: ```cpp if (command == "on") { digitalWrite(LED_BUILTIN, HIGH); } else if (command == "off") { digitalWrite(LED_BUILTIN, LOW); } ``` We can also send a response confirmation back with ```cpp client.println("Turned the LED " + command); ``` That's it! Now load the code on the Arduino and call the `/on` URL, or the `/off` URL. I reserved a static IP to the Arduino using my local network router, and I named it `arduino.local` in my `/etc/hosts` file, so reaching out to `http://arduino.local/on` turns the LED on, and to `http://arduino.local/off` turns the LED off. Here's the complete program: ```cpp #include #include WiFiServer server(80); void setup() { char ssid[] = SECRET_SSID; char pass[] = SECRET_PASS; Serial.begin(9600); while (!Serial); int status = WL_IDLE_STATUS; while (status != WL_CONNECTED) { Serial.print("Connecting to "); Serial.println(ssid); status = WiFi.begin(ssid, pass); delay(5000); } Serial.print("IP address: "); Serial.println(WiFi.localIP()); server.begin(); } void loop() { WiFiClient client = server.available(); if (client) { String line = ""; String command = ""; while (client.connected()) { if (client.available()) { char c = client.read(); Serial.write(c); if (c != '\n' && c != '\r') { line += c; } if (c == '\n') { if (line.length() == 0) { if (command == "on") { digitalWrite(LED_BUILTIN, HIGH); } else if (command == "off") { digitalWrite(LED_BUILTIN, LOW); } client.println("HTTP/1.1 200 OK"); client.println("Content-Type: text/html"); client.println("Connection: close"); client.println(); client.println(""); client.println(""); client.println("Turned the LED " + command); client.println(""); break; } else { if (line.startsWith("GET /on ")){ command = "on"; } if (line.startsWith("GET /off ")) { command = "off"; } line = ""; } } } } client.stop(); } } ```