diff --git a/frontend/components/dashboard/ScanTerminalDashboard.tsx b/frontend/components/dashboard/ScanTerminalDashboard.tsx
index 875d1e2f..81087fc6 100644
--- a/frontend/components/dashboard/ScanTerminalDashboard.tsx
+++ b/frontend/components/dashboard/ScanTerminalDashboard.tsx
@@ -12,6 +12,7 @@ import {
   Search,
   Table2,
   UserRound,
+  Users,
 } from "lucide-react";
 import { Fragment, useCallback, useEffect, useMemo, useRef, useState } from "react";
 import type { CityListItem, ProAccessState, ScanOpportunityRow } from "@/lib/dashboard-types";
@@ -388,6 +389,19 @@ function PolyWeatherTerminal({
   }, [searchInputRef, setSearchQuery]);
   const [navExpanded, setNavExpanded] = useState(false);
   const [activeNavKey, setActiveNavKey] = useState<string>("thresholds");
+  const [onlineCount, setOnlineCount] = useState<number | null>(null);
+
+  useEffect(() => {
+    const fetchOnline = () => {
+      fetch("/api/ops/online-users", { headers: { Accept: "application/json" } })
+        .then((r) => (r.ok ? r.json() : null))
+        .then((d) => { if (d?.online != null) setOnlineCount(d.online); })
+        .catch(() => {});
+    };
+    fetchOnline();
+    const id = setInterval(fetchOnline, 60_000);
+    return () => clearInterval(id);
+  }, []);
 
   const [gridCols, setGridCols] = useState<number>(() => {
     return getStoredGridSide("polyweather_terminal_grid_cols");
@@ -659,6 +673,12 @@ function PolyWeatherTerminal({
               <Activity size={13} />
               {t("dashboard", isEn)}
             </div>
+            {onlineCount != null && (
+              <div className="hidden items-center gap-1 text-[10px] font-medium text-slate-400 lg:flex">
+                <Users size={12} />
+                <span>{onlineCount}</span>
+              </div>
+            )}
           </div>
           <div className="flex items-center gap-2 text-xs text-slate-500">
             <span className="hidden font-mono md:inline text-slate-500">{userLocalTime}</span>
diff --git a/src/utils/online_tracker.py b/src/utils/online_tracker.py
new file mode 100644
index 00000000..749bd33e
--- /dev/null
+++ b/src/utils/online_tracker.py
@@ -0,0 +1,43 @@
+"""Lightweight online-user tracker.  Records last-seen timestamps in memory
+and exposes a count of users active within a sliding window.  No external
+dependency — just a dict + lock + periodic cleanup thread."""
+
+from __future__ import annotations
+
+import threading
+import time
+from typing import Dict
+
+_online_users: Dict[str, float] = {}
+_lock = threading.Lock()
+_cleanup_interval_sec = 120
+_window_sec = 300  # 5 minutes
+
+
+def _cleanup_stale() -> None:
+    cutoff = time.time() - _window_sec
+    with _lock:
+        stale = [uid for uid, ts in _online_users.items() if ts < cutoff]
+        for uid in stale:
+            del _online_users[uid]
+
+
+def _start_cleanup() -> None:
+    _cleanup_stale()
+    threading.Timer(_cleanup_interval_sec, _start_cleanup).start()
+
+
+_start_cleanup()
+
+
+def record_activity(user_id: str) -> None:
+    if not user_id:
+        return
+    with _lock:
+        _online_users[user_id] = time.time()
+
+
+def online_count() -> int:
+    _cleanup_stale()
+    with _lock:
+        return len(_online_users)
diff --git a/web/core.py b/web/core.py
index 94ad2f73..52a9f545 100644
--- a/web/core.py
+++ b/web/core.py
@@ -230,6 +230,8 @@ def _bind_optional_supabase_identity(request: Request) -> None:
     request.state.auth_email = identity.email
     request.state.auth_points = identity.points
     request.state.auth_created_at = identity.created_at
+    from src.utils.online_tracker import record_activity
+    record_activity(identity.user_id)
 
 
 def _resolve_auth_points(request: Request) -> int:
@@ -306,6 +308,8 @@ def _assert_entitlement(request: Request) -> None:
 
         request.state.auth_user_id = identity.user_id
         request.state.auth_email = identity.email
+        from src.utils.online_tracker import record_activity
+        record_activity(identity.user_id)
         return
 
     if not _ENTITLEMENT_GUARD_ENABLED:
diff --git a/web/routers/ops.py b/web/routers/ops.py
index dfc74f42..4313d887 100644
--- a/web/routers/ops.py
+++ b/web/routers/ops.py
@@ -29,6 +29,12 @@ from web.services.ops_api import (
 router = APIRouter(tags=["ops"])
 
 
+@router.get("/api/ops/online-users")
+async def ops_online_users():
+    from src.utils.online_tracker import online_count
+    return {"online": online_count()}
+
+
 @router.get("/api/ops/users")
 async def ops_search_users(request: Request, q: str = "", limit: int = 20):
     return search_ops_users(request, q=q, limit=limit)