RSSI (Received Signal Strength Indicator) is a useful metric for determining how strong the Wi-Fi signal is at your ESP8266’s location.

What You’ll Need:

• An ESP8266 board.
• A Wi-Fi network to connect to.

#include <ESP8266WiFi.h>

const char* ssid = "YOUR_WIFI_SSID";    
const char* password = "YOUR_WIFI_PASS";

void setup() {
  Serial.begin(115200);
  Serial.println();


  WiFi.begin(ssid, password);
  Serial.printf("Connecting to %s\n", ssid);

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

  Serial.println("\nConnected!");
}

void loop() {
  // Measure RSSI
  long rssi = WiFi.RSSI();
  Serial.printf("Signal Strength (RSSI): %ld dBm\n", rssi);

  delay(5000); // Wait 5 seconds before the next measurement
}

 
WiFi.RSSI(): Returns the RSSI value in dBm (decibels relative to 1 milliwatt).

• Closer to 0: Stronger signal (e.g., -30 dBm is excellent).
• Lower values: Weaker signal (e.g., -90 dBm is poor).