> For the complete documentation index, see [llms.txt](https://docs.cstplus.org/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.cstplus.org/documentation/guides/emergency-alert-system-eas.md).

# Emergency Alert System (EAS)

EAS lets you override your live channels with an emergency broadcast instantly. When activated, selected channels (or all channels) switch to the alert feed and stay there until you cancel.

{% hint style="warning" %}
EAS is available on **Pro and Business** plans. The EAS settings tab is not shown on Starter.
{% endhint %}

***

### How it works

CST+ monitors configured alert sources every 30 seconds. When a matching alert appears, or when you trigger one manually, the edge redirects the affected channels to a shared alert HLS output. The switch happens at the next HLS segment boundary: typically within **2-6 seconds**.

When the alert is cancelled, channels switch back to their normal streams at the next segment boundary. No restart needed.

***

### Configuration

Go to **Settings > EAS**.

#### Alert content

First, configure what plays during an alert:

{% tabs %}
{% tab title="Video file" %}
Upload an MP4 to loop during the alert (e.g. an emergency graphic with an audio tone). The file loops for as long as the alert is active.
{% endtab %}

{% tab title="Live HLS source" %}
Point EAS at an external HLS URL (e.g. a government emergency broadcast feed). CST+ will relay that stream to all affected channels.
{% endtab %}
{% endtabs %}

{% hint style="danger" %}
If no alert content is configured, EAS will activate but viewers will see a black screen. Always set up alert content before enabling automatic alert sources.
{% endhint %}

#### Alert sources

| Source                         | Covers                                              |
| ------------------------------ | --------------------------------------------------- |
| NWS (National Weather Service) | US weather alerts. Filter by type and state/county. |
| USGS Earthquakes               | Earthquakes above a magnitude threshold you set.    |
| USGS Volcanoes                 | Volcanic activity alerts.                           |
| GDACS                          | Global disaster alerts for international audiences. |

#### Channel scope

| Option            | What it does                                                       |
| ----------------- | ------------------------------------------------------------------ |
| All channels      | Every channel on this server switches to the alert feed            |
| Selected channels | Only specific channels are overridden; others keep airing normally |

#### Readiness check

Click **Check readiness** before saving. CST+ verifies that the alert HLS output is accessible and that the alert content file is valid.

{% hint style="success" %}
Run the readiness check after every EAS configuration change, not just at initial setup. This catches broken URLs or missing files before an actual emergency.
{% endhint %}

***

### Manual trigger

{% tabs %}
{% tab title="From the panel" %}
Go to **Settings > EAS** and click **Activate EAS** or **Cancel EAS**.

The red EAS banner appears in the admin panel header whenever an alert is active.
{% endtab %}

{% tab title="Via API" %}
Trigger:

```bash
POST /api/eas/trigger
Authorization: Bearer YOUR_API_KEY
```

Cancel:

```bash
POST /api/eas/cancel
Authorization: Bearer YOUR_API_KEY
```

{% endtab %}
{% endtabs %}

***

### EAS in fleet mode

EAS activation on the primary propagates to all online edge nodes automatically.

{% hint style="warning" %}
Edge nodes that are offline when EAS is triggered will switch over when they reconnect and re-sync with the primary. A reconnecting edge always inherits the current alert state.
{% endhint %}


---

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