diff --git a/firmware/esp32/overland-controller/overland-controller.ino b/firmware/esp32/overland-controller/overland-controller.ino
index 8cc5cb6..01d6227 100644
--- a/firmware/esp32/overland-controller/overland-controller.ino
+++ b/firmware/esp32/overland-controller/overland-controller.ino
@@ -918,6 +918,23 @@ async function relay(id,on){
     },1500);
   }
 }
+function formatUptime(totalSeconds){
+  totalSeconds=Math.max(0,Math.floor(Number(totalSeconds)||0));
+  const days=Math.floor(totalSeconds/86400);
+  totalSeconds%=86400;
+  const hours=Math.floor(totalSeconds/3600);
+  totalSeconds%=3600;
+  const minutes=Math.floor(totalSeconds/60);
+  const seconds=totalSeconds%60;
+
+  const parts=[];
+  if(days) parts.push(days+"d");
+  if(days||hours) parts.push(hours+"h");
+  if(days||hours||minutes) parts.push(minutes+"m");
+  parts.push(seconds+"s");
+  return parts.join(" ");
+}
+
 function render(data){
   data=mergeStatus(window.lastStatus,data);
   window.lastStatus=data;
@@ -996,7 +1013,7 @@ function render(data){
   $("wifiIp").textContent=n.sta_ip||"--";
   $("apIp").textContent=n.ap_ip||"--";
   $("fw").textContent=(s.firmware_name||"--")+" "+(s.firmware_version||"");
-  $("uptime").textContent=(s.uptime_seconds||0)+" sec";
+  $("uptime").textContent=formatUptime(s.uptime_seconds||0);
   renderConfigControls(data);
   populateSetupFields(data);
 }
diff --git a/tests/test_http_api_contract.py b/tests/test_http_api_contract.py
index a544422..02cf10e 100644
--- a/tests/test_http_api_contract.py
+++ b/tests/test_http_api_contract.py
@@ -552,3 +552,15 @@ def test_embedded_webui_temp_config_uses_mobile_cards():
     assert "Weather Badge" in body
     assert "configrow tempConfigRow" not in body
     assert "Address:" not in body
+
+
+def test_embedded_webui_formats_uptime():
+    source = firmware_source()
+
+    assert "function formatUptime(totalSeconds)" in source
+    assert 'parts.push(days+"d")' in source
+    assert 'parts.push(hours+"h")' in source
+    assert 'parts.push(minutes+"m")' in source
+    assert 'parts.push(seconds+"s")' in source
+    assert 'formatUptime(s.uptime_seconds||0)' in source
+    assert '+" sec"' not in source