diff --git a/lib/www/client/source/src/views/Map.vue b/lib/www/client/source/src/views/Map.vue
index 993e34b..9d8d426 100644
--- a/lib/www/client/source/src/views/Map.vue
+++ b/lib/www/client/source/src/views/Map.vue
@@ -475,7 +475,7 @@ export default {
         bounds._northEast.lng,
         bounds._northEast.lat
       ].map(i => i.toFixed(bboxScale)).join(",");
-      const limit = 10000;
+      const limit = 10000; // Empirical value
 
       const query = new URLSearchParams({bbox, limit});
 
@@ -521,7 +521,9 @@ export default {
 
               l.layer.lastRequestURL = url;
             } else {
-              console.warn("Too much data from", url);
+              console.warn(`Too much data from ${url} (${layer.features.length ?? layer.length} ≥ ${limit} features)`);
+
+              this.showSnack([`Layer ‘${l.layer.options.userLayerName}’ is too large: ${layer.features.length ?? layer.length} features; maximum is ${limit}`, "error"]);
             }
           })
           .finally( () => {
@@ -783,7 +785,7 @@ export default {
       this.addUserLayers(userLayers);
     },
 
-    ...mapActions(["api"])
+    ...mapActions(["api", "showSnack"])
 
   },