How to fix ESP32 WiFi “connection failed” or weak signal problems

WiFi failures look like “code problems,” but a lot of the time it's just physics: distance, walls, interference, and a tiny antenna on a dev board.

Check signal strength (RSSI)

RSSI is reported in dBm. Closer to 0 is stronger. Rough guide:

-40 to -60 dBm: solid
-60 to -70 dBm: usually OK
-70 to -80 dBm: flaky
worse than -80 dBm: expect dropouts

esp32_wifi_rssi.ino

cpp

#include <WiFi.h>

const char* ssid = "YOUR_WIFI_NAME";
const char* password = "YOUR_WIFI_PASSWORD";

void setup() {
  Serial.begin(115200);
  delay(200);
  WiFi.mode(WIFI_STA);
  WiFi.setSleep(false);
  WiFi.begin(ssid, password);

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

void loop() {
  Serial.print("RSSI: ");
  Serial.print(WiFi.RSSI());
  Serial.println(" dBm");
  delay(2000);
}

Fixes that actually move the needle

Move the ESP32. A 30cm move can be the difference between -78 and -62 dBm.
Keep it away from metal and wiring bundles. Enclosures and big ground planes can detune the antenna.
Try a different channel. 2.4GHz is crowded; channel 1/6/11 are the usual options.
Use a better access point location or add a mesh node closer.

Common “router settings” gotchas

Band steering can confuse some clients. If your router has separate 2.4/5 SSIDs, use the 2.4 SSID.
WPA3-only can cause failures. Try WPA2/WPA3 mixed.
Guest networks sometimes block IoT-style traffic.

Bottom line

If RSSI is worse than about -70 dBm, fix the signal first: placement, channel, and access point location. Once the link is stable, the code usually “magically” works.