diff --git a/README.md b/README.md
index 049e681..42c839e 100644
--- a/README.md
+++ b/README.md
@@ -77,6 +77,19 @@ After connecting, the device is reachable at:
 - `http://m1730.local` (mDNS, works on most local networks)
 - `http://<IP address>` (shown in the serial monitor on boot)
 
+### Factory reset (forgot password)
+
+If you lose the web UI password, hold the **BOOT button** (GPIO0) for 3 seconds during startup. The firmware resets all settings to factory defaults **except** meter pin assignments and calibration (maxDuty), which are preserved. On acknowledgement, all connected meters sweep 0→100→0.
+
+Serial output confirms the reset:
+
+```
+[BOOT] BOOT button held, hold 3s for factory reset...
+[BOOT] factory reset triggered!
+...
+[BOOT] factory reset complete, restarting...
+```
+
 ---
 
 ## Web UI
@@ -223,4 +236,4 @@ Config is stored as JSON in LittleFS at `/config.json`.
 }
 ```
 
-The file is written by the web UI and should not need manual editing. To reset to factory defaults, delete the file or erase flash with `pio run --target erase`.
+The file is written by the web UI and should not need manual editing. To reset to factory defaults (keeping pin/calibration), hold the BOOT button for 3 seconds at startup. To erase everything including flash, use `pio run --target erase`.
diff --git a/src/main.cpp b/src/main.cpp
index 61986fa..da3d82d 100644
--- a/src/main.cpp
+++ b/src/main.cpp
@@ -477,7 +477,7 @@ static void handleRoot() {
   html += ".count-row label{margin-bottom:4px}";
   html += ".btn{width:100%;margin-top:8px;padding:12px;background:#4361ee;color:#fff;border:none;border-radius:8px;font-size:15px;font-weight:600;cursor:pointer;transition:background .2s}";
   html += ".btn:hover{background:#3651d4}.mac{font-size:12px;color:#999;text-align:center;margin-top:20px}";
-html += ".tgl-lbl{margin-bottom:0!important;line-height:18px}.switch{position:relative;display:inline-block;width:32px;height:18px;margin-left:auto;flex-shrink:0}";
+html += ".tgl-lbl{margin-bottom:0!important;line-height:18px}.switch{position:relative;display:inline-block;width:32px;height:18px;margin-left:auto;flex-shrink:0}fieldset .row label.switch{width:32px}";
 html += ".switch input{opacity:0;width:0;height:0}.slid{position:absolute;cursor:pointer;top:0;left:0;right:0;bottom:0;background:#ccc;border-radius:18px;transition:.3s}";
 html += ".slid::before{content:\"\";position:absolute;height:14px;width:14px;left:2px;top:2px;background:#fff;border-radius:50%;transition:.3s;box-shadow:0 1px 3px rgba(0,0,0,.2)}";
 html += ".switch input:checked+.slid{background:#4361ee}.switch input:checked+.slid::before{transform:translateX(14px)}";
@@ -612,6 +612,109 @@ static void startServer() {
   Serial.println("HTTP server started");
 }
 
+// ---------------------------------------------------------------------------
+// Factory reset (hold BOOT button 3s at startup)
+// ---------------------------------------------------------------------------
+
+static void factoryReset() {
+  Serial.println("[BOOT] factory reset triggered!");
+
+  int count = meterCount;
+  int pins[MAX_METERS];
+  float maxD[MAX_METERS];
+  float cur[MAX_METERS];
+  for (int i = 0; i < count; i++) {
+    pins[i] = meters[i].pin;
+    maxD[i] = meters[i].maxDuty;
+    cur[i] = meters[i].currentValue;
+  }
+
+  // Reset hostname, auth, MQTT, meter metadata
+  strlcpy(hostname, HOSTNAME_DEFAULT, sizeof(hostname));
+  hostnameParam.setValue(hostname, strlen(hostname));
+
+  authCfg.enabled = false;
+  authCfg.pass[0] = '\0';
+
+  mqttCfg.enabled = false;
+  mqttCfg.host[0] = '\0';
+  mqttCfg.port = 1883;
+  mqttCfg.user[0] = '\0';
+  mqttCfg.pass[0] = '\0';
+  strlcpy(mqttCfg.prefix, "m1730", sizeof(mqttCfg.prefix));
+
+  for (int i = 0; i < MAX_METERS; i++) {
+    meters[i].pin = 0;
+    meters[i].maxDuty = 0;
+    meters[i].currentValue = 0;
+    meters[i].name[0] = '\0';
+    meters[i].unit[0] = '\0';
+    meters[i].rangeMin = 0.0;
+    meters[i].rangeMax = 100.0;
+  }
+
+  // Restore pins, calibration, current state
+  for (int i = 0; i < count; i++) {
+    meters[i].pin = pins[i];
+    meters[i].maxDuty = maxD[i];
+    meters[i].currentValue = cur[i];
+  }
+
+  saveConfig();
+
+  // Attach meters temporarily for the sweep acknowledgement
+  for (int i = 0; i < count && i < 8; i++) {
+    if (meters[i].pin > 0) {
+      ledcSetup(i, PWM_FREQ, PWM_RES);
+      ledcAttachPin(meters[i].pin, i);
+    }
+  }
+
+  // Sweep 0→100→0 over ~2 seconds
+  const int steps = 20;
+  for (int phase = 0; phase < 2; phase++) {
+    for (int s = 0; s <= steps; s++) {
+      float pct = (phase == 0) ? (float)s / steps * 100.0f : (float)(steps - s) / steps * 100.0f;
+      for (int i = 0; i < count && i < 8; i++) {
+        if (meters[i].pin > 0 && meters[i].maxDuty > 0) {
+          float duty = pct / 100.0f * meters[i].maxDuty / 100.0f;
+          ledcWrite(i, constrain((int)(duty * 1023), 0, 1023));
+        }
+      }
+      delay(50);
+    }
+  }
+
+  // Restore current values
+  for (int i = 0; i < count && i < 8; i++) {
+    if (meters[i].pin > 0 && meters[i].maxDuty > 0) {
+      float pct = cur[i] / 100.0f * meters[i].maxDuty / 100.0f;
+      ledcWrite(i, constrain((int)(pct * 1023), 0, 1023));
+    }
+  }
+
+  Serial.println("[BOOT] factory reset complete, restarting...");
+  delay(200);
+  ESP.restart();
+}
+
+static void checkFactoryReset() {
+  pinMode(0, INPUT_PULLUP);
+  delay(10);
+  if (digitalRead(0) == LOW) {
+    Serial.println("[BOOT] BOOT button held, hold 3s for factory reset...");
+    unsigned long start = millis();
+    while (millis() - start < 3000) {
+      delay(50);
+      if (digitalRead(0) != LOW) {
+        Serial.println("[BOOT] factory reset aborted (button released)");
+        return;
+      }
+    }
+    factoryReset();
+  }
+}
+
 // ---------------------------------------------------------------------------
 // Setup & loop
 // ---------------------------------------------------------------------------
@@ -624,6 +727,8 @@ void setup() {
   loadConfig();
   hostnameParam.setValue(hostname, strlen(hostname));
 
+  checkFactoryReset();
+
   attachMeters();
   applyMeters();