diff --git a/README.md b/README.md
index c994646..529181a 100644
--- a/README.md
+++ b/README.md
@@ -53,8 +53,14 @@ code lives in `src/main.js` with a class-based architecture:
 
 - **11 WAN hosts**: datavi.be, Anthropic API, OpenAI API, AWS, GCP, Azure,
   DigitalOcean, Cloudflare, Fastly, Akamai, GitHub
-- **1 Local host**: Local Gateway (192.168.100.1), tracked separately from WAN
-  stats
+- **Local CPE**: Cable modem at 192.168.100.1 (always monitored)
+- **Local Gateway**: Auto-detected on startup by probing common default gateway
+  addresses (192.168.1.1, 192.168.0.1, 192.168.8.1, 10.0.0.1); first responder
+  wins. Note: modern browsers enforce Private Network Access restrictions that
+  block public-origin pages from reaching RFC1918 addresses, so local targets
+  only work when NetWatch is served from localhost or a private address.
+
+Local hosts are tracked separately from WAN stats.
 
 ### Latency measurement
 
diff --git a/src/main.js b/src/main.js
index b817cdc..1dd4a2e 100644
--- a/src/main.js
+++ b/src/main.js
@@ -2,6 +2,9 @@ import "./styles.css";
 
 // --- Configuration -----------------------------------------------------------
 
+// Timing, axis labels, and display constants. Latency above maxLatency is
+// clamped to "unreachable". The history buffer holds maxHistoryPoints
+// samples (historyDuration / updateInterval).
 const CONFIG = Object.freeze({
     updateInterval: 2000,
     historyDuration: 300,
@@ -15,6 +18,9 @@ const CONFIG = Object.freeze({
     },
 });
 
+// WAN endpoints to monitor. These are used for the aggregate health/stats
+// display (min/max/avg). Ordered: personal, LLM APIs, big-3 cloud, then
+// CDN/hosting/other.
 const WAN_HOSTS = [
     { name: "datavi.be", url: "https://datavi.be" },
     { name: "Anthropic API", url: "https://api.anthropic.com" },
@@ -29,7 +35,55 @@ const WAN_HOSTS = [
     { name: "GitHub", url: "https://github.com" },
 ];
 
-const LOCAL_HOSTS = [{ name: "Local Gateway", url: "http://192.168.100.1" }];
+// The cable modem / CPE upstream of the local gateway — always monitored.
+const LOCAL_CPE = { name: "Local CPE", url: "http://192.168.100.1" };
+
+// Common default gateway addresses. On startup we probe each one and use
+// whichever responds first as the "Local Gateway" monitor target.
+//
+// NOTE: Modern browsers enforce Private Network Access (PNA) restrictions
+// that block pages served from public origins from making requests to
+// RFC1918 addresses. These local targets will likely only work when
+// NetWatch is served from localhost or another private address.
+const GATEWAY_CANDIDATES = [
+    "http://192.168.1.1",
+    "http://192.168.0.1",
+    "http://192.168.8.1",
+    "http://10.0.0.1",
+];
+
+// --- Gateway Detection -------------------------------------------------------
+
+// Probe each gateway candidate with a short timeout. Returns the first one
+// that responds, or null if none do. We race them all in parallel and take
+// whichever wins.
+async function detectGateway() {
+    try {
+        const result = await Promise.any(
+            GATEWAY_CANDIDATES.map(async (url) => {
+                const controller = new AbortController();
+                const timeoutId = setTimeout(() => controller.abort(), 1500);
+                try {
+                    await fetch(url, {
+                        method: "HEAD",
+                        mode: "no-cors",
+                        cache: "no-store",
+                        signal: controller.signal,
+                    });
+                    clearTimeout(timeoutId);
+                    return { name: "Local Gateway", url };
+                } catch {
+                    clearTimeout(timeoutId);
+                    throw new Error("no response");
+                }
+            }),
+        );
+        return result;
+    } catch {
+        // All candidates failed
+        return null;
+    }
+}
 
 // --- App State ---------------------------------------------------------------
 
@@ -75,9 +129,9 @@ class HostState {
 }
 
 class AppState {
-    constructor() {
+    constructor(localHosts) {
         this.wan = WAN_HOSTS.map((h) => new HostState(h));
-        this.local = LOCAL_HOSTS.map((h) => new HostState(h));
+        this.local = localHosts.map((h) => new HostState(h));
         this.paused = false;
     }
 
@@ -543,8 +597,13 @@ function handleResize(state) {
 
 // --- Bootstrap ---------------------------------------------------------------
 
-function init() {
-    const state = new AppState();
+async function init() {
+    // Probe common gateway IPs to find the local router
+    const gateway = await detectGateway();
+    const localHosts = [LOCAL_CPE];
+    if (gateway) localHosts.push(gateway);
+
+    const state = new AppState(localHosts);
     buildUI(state);
 
     document