# Alert on detections

Send email, webhook, or push notification alerts when your vision service detects specific objects or classifications.
> Source: https://docs.viam.com/vision/object-detection/alert-on-detections/


You want to be notified when your camera detects something specific: a person in a restricted area, a missing hard hat, or an anomaly on a production line. This guide shows you how to connect your vision service to Viam's trigger system so you receive an email, webhook, or push notification whenever a detection occurs. No custom code is required.

## Concepts

### The alert pipeline

The alert system chains three resources together:

1. **Filtered camera**: a camera module that only passes images to the data management service when specific detections or classifications are present.
2. **Data management service**: captures images from the filtered camera and syncs them to the Viam cloud.
3. **Trigger**: fires when new data syncs, sending an email, webhook, or push notification.

Because the filtered camera only passes images that match your criteria, every synced image represents a detection event. The trigger fires on each sync, turning data events into alerts.

### Filtered camera behavior

The [`filtered-camera`](https://app.viam.com/module/viam/filtered-camera) module wraps an existing camera and applies a vision service as a filter. It functions as a normal camera for live viewing and API calls. The filtering only affects what gets captured by the data management service.

You configure the filter with:

- **A label**: the detection or classification class name to look for (such as "Person" or "NO-Hardhat").
- **A confidence threshold** (0.0-1.0): the minimum confidence score required. Only images where the model meets this threshold are captured.

### Alert frequency

Triggers support a configurable alert frequency to prevent alert fatigue. For example, you can limit alerts to a maximum of one per hour even if detections occur continuously.

## Steps

### 1. Configure a filtered camera

Add the filtered camera module to your machine:

1. Navigate to your machine's **CONFIGURE** tab.
2. Click **+** and select **Blocks**.
3. In the search field, type `filtered-camera` and select the matching result.
4. Click **Add to machine**, name the component `objectfilter-cam`, and click **Add to machine** again to confirm. The module is installed automatically.
5. Add configuration attributes:

   


### Template

Replace `<camera_name>` and `<vision_service_name>` with the names of your camera and vision service. Choose either `objects` (for bounding-box detections) or `classifications` (for image-level labels) and remove the other.

```json
{
  "camera": "<camera_name>",
  "vision_services": [
    {
      "vision": "<vision_service_name>",
      "classifications": { "<label>": 0.5 },
      "objects": { "<label>": 0.5 }
    }
  ]
}
```

### Example: Hard hat detection

This example uses a YOLOv8 model named `yolo` to detect workers without hard hats:

```json
{
  "camera": "my_webcam",
  "vision_services": [
    {
      "vision": "yolo",
      "objects": {
        "NO-Hardhat": 0.6
      }
    }
  ]
}
```



6. Click **Save**.

For a fuller walkthrough that combines the filtered camera with an ML detector, see [Filter images at the edge](/data/filter-at-the-edge/#use-a-filtered-camera-with-ml). The [`filtered-camera` module README](https://app.viam.com/module/viam/filtered-camera) has the raw attribute reference.

> **Tip:**
> 
> To verify your confidence threshold, expand the **TEST** panel on your vision service card, select the right camera in the **Camera** dropdown, and observe the confidence levels for live detections.

### 2. Configure data capture and sync

Add the data management service to capture and sync filtered images:

1. Click **+** and select **Blocks**.
2. In the search field, type `data management` and select `data_manager/builtin` from the results.
3. Click **Add to machine**, name the service `data-manager`, and click **Add to machine** again to confirm.
4. Leave the default attributes and click **Save**.

Enable data capture on the filtered camera:

1. Locate the `objectfilter-cam` panel.
2. Click the **Data Capture** button.
3. Set **Method** to **GetImages**.
4. Set **Frequency (hz)** to `0.2` (one image every 5 seconds). Adjust as needed for your use case.

### 3. Configure a trigger

Add a trigger to send alerts when filtered images sync:

1. Click **+** in the left sidebar and select **Trigger**.
2. Enter a name and click **Create**.
3. Set **Type** to **Data has been synced to the cloud**.
4. Set **Data Types** to **Binary (image)**.
5. Add notification methods. The following options live in the **Email**, **Webhook**, and **Push notifications** sections of the trigger card:

   **Email**: In the **Email** section, toggle **Send to specific users** on, enter each email address, and set the **Alert frequency** per row. Or toggle **Send to all machine owners** on and set the **Alert frequency** for the all-owners row.

   **Webhook**: In the **Webhook** section click **Add webhook**, enter the URL of your cloud function, and implement logic to process the [webhook payload](/reference/triggers/#webhook-attributes). Use this to integrate with external services like Twilio, PagerDuty, or Zapier.

   **Push notifications**: In the **Push notifications** section click **Add push notifications**. Choose the **Application** (Viam mobile or a custom app ID). Then toggle **Send to all machine owners** on, or toggle **Send to specific users** on, add each recipient's **User email**, and click **Add user**. Recipients must be machine owners or operators. Set the **Alert frequency**.

6. Set each **Alert frequency** you enabled (for example, maximum one alert per hour).
7. Click **Save**.

## Try it

Before trying the end-to-end flow, confirm you have all three pieces from above saved on the machine: the filtered camera (step 1), the data management service plus data capture on the filtered camera (step 2), and the trigger with at least one notification method (step 3). The flow does not work unless all three are configured together.

1. Point your camera at an object your model recognizes and wait for the capture interval to pass.
2. Check the **TEST** panel on your vision service to confirm detections are occurring with sufficient confidence.
3. Navigate to the **DATA** tab and verify that images are syncing.
4. Check your email, webhook endpoint, or mobile app for the alert.

## Troubleshooting

**No alerts received**



- Check the **LOGS** tab for errors from the filtered camera or data management service.
- Verify your vision service detects objects with confidence above your threshold using the **TEST** panel.
- Confirm the label in your filtered camera config exactly matches the vision service output (case-sensitive).
- Check the **DATA** tab to see if images are being captured and synced.
- Verify trigger configuration: correct type (data synced), correct data type (binary/image), and valid notification settings.




**Too many alerts**



- Increase the confidence threshold in the filtered camera configuration to reduce false positives.
- Lower the data capture frequency (for example, from `0.2` to `0.1` images per second).
- Increase the alert frequency limit in the trigger settings (for example, maximum one per hour).




**Images syncing but no trigger fires**



- Confirm the trigger is configured with **Data has been synced to the cloud** as the type.
- Check that **Binary (image)** is selected as the data type.
- Verify that at least one notification method (email, webhook, or push notification) is configured.




## What's next

- [Act on detections](/vision/object-detection/act-on-detections/): build a module that responds to vision results in real time.
- [Triggers reference](/reference/triggers/): full documentation for trigger types, webhook payloads, and configuration options.
- [Capture and sync data](/data/capture-sync/capture-and-sync-data/): learn more about configuring data capture and sync intervals.