diff --git a/app/processors/stats.py b/app/processors/stats.py
index 0a2c893..cb1ed26 100644
--- a/app/processors/stats.py
+++ b/app/processors/stats.py
@@ -5,4 +5,4 @@ from app import app
 @app.before_request
 def request_time():
     g.request_start_time = time()
-    g.request_time = lambda: "%.5fs" % (time() - g.request_start_time)
+    g.request_time = lambda: time() - g.request_start_time
diff --git a/app/static/css/header.css b/app/static/css/header.css
index a75f8b4..fbeaf70 100644
--- a/app/static/css/header.css
+++ b/app/static/css/header.css
@@ -85,3 +85,15 @@ header .form input[type="search"]:focus ~ a {
 #spotlight a {
 	display: block;
 }
+
+
+#server-speed-warning {
+	background: var(--warn);
+	color: var(--warn-text);
+	text-align: center;
+	border-radius: 2px;
+	padding: 4px;
+	margin: 0 8px;
+	font-weight: bold;
+	text-shadow: 0 1px 1px rgba(0,0,0,.5);
+}
diff --git a/app/templates/base/footer.html b/app/templates/base/footer.html
index aa30d5a..8f09472 100644
--- a/app/templates/base/footer.html
+++ b/app/templates/base/footer.html
@@ -2,7 +2,7 @@
 	<p>Planète Casio est un site communautaire non affilié à CASIO. Toute reproduction de Planète Casio, même partielle, est interdite.</p>
 	<p>Les programmes et autres publications présentes sur Planète Casio restent la propriété de leurs auteurs et peuvent être soumis à des licences ou des copyrights.</p>
 	{% if current_user.is_authenticated and current_user.priv('misc.dev-infos') %}
-		<p>Page générée en {{ g.request_time() }}</p>
+		<p>Page générée en {{ "%.3f" % g.request_time() }} secondes.</p>
 	{% endif %}
 	<p>Ceci est un environnement de test. Tout contenu peut être supprimé sans avertissement préalable.</p>
 </footer>
diff --git a/app/templates/base/header.html b/app/templates/base/header.html
index 46d25a0..932bae6 100644
--- a/app/templates/base/header.html
+++ b/app/templates/base/header.html
@@ -11,3 +11,10 @@
 <div id="spotlight">
 	<a href="#" class="button bg-error">Jeu du mois : février 2019</a>
 </div>
+
+{% if current_user.is_authenticated and current_user.priv('misc.dev-infos') %}
+  {% set reqtime = g.request_time() %}
+  {% if reqtime > V5Config.SLOW_REQUEST_THRESHOLD %}
+		<div id="server-speed-warning">Génération<br>{{ "%.3f" % reqtime }} s</div>
+	{% endif %}
+{% endif %}
diff --git a/config.py b/config.py
index b666f25..8b4efe8 100644
--- a/config.py
+++ b/config.py
@@ -55,6 +55,10 @@ class DefaultConfig(object):
     GLADOS_PORT = 5555
     # Time before trigerring the necropost alert
     NECROPOST_LIMIT = timedelta(days=31)
+    # Acceptable page loading time; longer generation is reported to devs. This
+    # is computed in the page header, so it doesn't account for most of the
+    # template generation.
+    SLOW_REQUEST_THRESHOLD = 0.400 # s
 
 
 class V5Config(LocalConfig, DefaultConfig):