diff --git a/README.md b/README.md
index c49c53ece..1be14d337 100644
--- a/README.md
+++ b/README.md
@@ -377,7 +377,7 @@ Twenty layers and map sources. **Eighteen have a keyless path.** Some offer addi
 | 🌍 **Earthquakes**          | Global seismic activity, last 24h                                                                                                                                                                                                                                                                                                                                                   | USGS                                    | 🟢                                                                                                  |
 | ◍ **Air quality**           | Live AQHI on the published 1–10+ health-risk scale, with a Weather-panel card showing the band legend and the highest readings in view. **Canada only** — ECCC is the first registered provider | ECCC MSC GeoMet                          | 🟢                                                                                                  |
 | 🚗 **Traffic**              | Simulated vehicles on OSM roads. With TomTom, live flow speeds drive the simulation and congestion colors below ~8 km; individual vehicle positions are not live observations                                                                                                                                                                                                       | TomTom + OSM                            | 🟢 simulation · 🟡 live flow speeds                                                                 |
-| 📹 **CCTV Mesh**            | ~4,000 public cameras (shared cap) projected _into_ the 3D space — Austin · Texas (TxDOT) · California (Caltrans) · London (TfL) · Ontario (511) · Finland (Fintraffic) · British Columbia (DriveBC) · Estonia (Tallinn, Tarktee) · Delaware (DelDOT live video) · New South Wales (Live Traffic NSW) · Calgary · Norway (Statens vegvesen) · Toronto · King County (WA) · Washington (WSDOT) · Catalonia (Servei Català de Trànsit), plus opt-in New York City (NYC DOT TMC, needs your own NYC DOT agreement) and opt-in Lithuania (Via Lietuva / Eismoinfo, photo licence unconfirmed). Positions are published; poses are estimated priors **you calibrate by dragging a gizmo on the camera itself** | City APIs                               | 🟢                                                                                                  |
+| 📹 **CCTV Mesh**            | ~4,000 public cameras (shared cap) projected _into_ the 3D space — Austin · Texas (TxDOT) · California (Caltrans) · London (TfL) · Ontario (511, free developer key) · Finland (Fintraffic) · British Columbia (DriveBC) · Estonia (Tallinn, Tarktee) · Delaware (DelDOT live video) · New South Wales (Live Traffic NSW) · Calgary · Norway (Statens vegvesen) · Toronto · King County (WA) · Washington (WSDOT) · Catalonia (Servei Català de Trànsit), plus opt-in New York City (NYC DOT TMC, needs your own NYC DOT agreement) and opt-in Lithuania (Via Lietuva / Eismoinfo, photo licence unconfirmed). Positions are published; poses are estimated priors **you calibrate by dragging a gizmo on the camera itself** | City APIs                               | 🟢                                                                                                  |
 | 📷 **Mapped ALPR Cameras**  | License-plate-reader camera locations tagged by OpenStreetMap contributors, loaded one city-sized view at a time, with **SHOW NEAREST**. Locations and tags only: no plate data, no video                                                                                                                                                                                           | OpenStreetMap (incl. DeFlock mapping)   | 🟢                                                                                                  |
 | 📷 **Street Level**         | Street-level photos behind one panel, one chip per provider: coverage on the streets, image cones, an embedded viewer and **FOLLOW**. Mapillary, Google Street View, KartaView and Panoramax | Mapillary · Google · KartaView · Panoramax | 🟢 KartaView, Panoramax · 🟡 Mapillary token · 🔴 Google Maps key |
 | 📻 **Radio**                | Geolocated world radio with an **analog tuner** — drag the needle across up to 750 stations and the globe flies to each broadcaster                                                                                                                                                                                                                                                 | Radio Browser / broadcasters            | 🟢                                                                                                  |
diff --git a/server/providers/cctv/ontario511.test.mjs b/server/providers/cctv/ontario511.test.mjs
index d654cf8be..d0cb1f73e 100644
--- a/server/providers/cctv/ontario511.test.mjs
+++ b/server/providers/cctv/ontario511.test.mjs
@@ -60,6 +60,6 @@ test('a rejected key is reported by status, never by the key itself', async (t)
     { ONTARIO_511_API_KEY: 'secret-key-value' },
   );
   assert.deepEqual(cameras, []);
-  assert.match(warnings.join('\n'), /400/);
+  assert.match(warnings.join('\n'), /400 \(check ONTARIO_511_API_KEY\)/);
   assert.doesNotMatch(warnings.join('\n'), /secret-key-value/);
 });
diff --git a/server/providers/cctv/sources.js b/server/providers/cctv/sources.js
index 7c048c68f..fe8b150b7 100644
--- a/server/providers/cctv/sources.js
+++ b/server/providers/cctv/sources.js
@@ -539,7 +539,14 @@ export async function loadOntarioSourcesFromOpenData(
       signal: AbortSignal.timeout(CCTV_SOURCE_FETCH_TIMEOUT_MS),
     });
     if (!resp.ok) {
-      console.warn('[CCTV] Ontario 511 camera download failed:', resp.status);
+      // The API answers 400 "Invalid Key" to a wrong or revoked key.
+      console.warn(
+        '[CCTV] Ontario 511 camera download failed:',
+        resp.status,
+        resp.status === 400 || resp.status === 401 || resp.status === 403
+          ? '(check ONTARIO_511_API_KEY)'
+          : '',
+      );
       return [];
     }
     const rows = await resp.json();