---
title: Detecting Inactive Devices With Notehub Smart Fleets
description: Learn a workflow for automatically sorting inactive devices into a custom Notehub fleet
source_url: https://dev.blues.io/blog/inactive-devices-smart-fleets/
canonical_url: https://dev.blues.io/blog/inactive-devices-smart-fleets/
markdown_url: https://dev.blues.io/blog/inactive-devices-smart-fleets.md
---

# Detecting Inactive Devices With Notehub Smart Fleets

![Detecting Inactive Devices With Notehub Smart Fleets banner](https://dev.blues.io/images/blog/posts/inactive-devices-smart-fleets/banner.jpg?v=ce4b7983)

January 20, 2026

## Learn a workflow for automatically sorting inactive devices into a custom Notehub fleet

- [Notehub](https://dev.blues.io/blog/tag/notehub)

[![TJ VanToll](https://dev.blues.io/images/blog/authors/tj-vantoll.jpg?v=c3d7f336)](https://dev.blues.io/blog/author/tj-vantoll/)

[TJ VanTollPrincipal Developer Advocate](https://dev.blues.io/blog/author/tj-vantoll/)

Today I want to show you a workflow you can use to detect and group inactive devices in your Notehub project. When in place, you’ll have a live-updating fleet that only includes devices Notehub hasn’t seen within a configurable time window.

Let’s look at how it works.

## Step 1: Create Two Fleets

This workflow revolves around fleets, and to set it up for yourself you’ll need to create two of them.

**All Devices**

Your first fleet needs to contain all devices on your Notehub project. There’s a good chance you already have a fleet like this, because by default Notehub autoprovisions all new devices into a fleet named “My Fleet”.

Visit your project’s **Settings** page to see if you still have a fleet like this in place. If not, you’ll need to create one and add all your devices to it. I like calling my fleet “All Devices”, but you can use any name you’d like.

![Default Notehub fleet location](https://dev.blues.io/images/blog/posts/inactive-devices-smart-fleets/default-fleet.png?v=d1fc1dec)

**Inactive Devices**

Next, create a second fleet named **Inactive** (or your name of choice). Eventually this fleet will contain only your inactive devices, but you can create it with just the default settings for now.

![Fleet for inactive devices](https://dev.blues.io/images/blog/posts/inactive-devices-smart-fleets/inactive-fleet.png?v=9e9b9d95)

## Step 2: Enable Watchdog Events

With your fleets created your next step is to enable [watchdog events](https://dev.blues.io/notehub/notehub-walkthrough.md#using-watchdog-events). In Notehub, watchdog events are a fleet-level feature that allow you to get notified when a device has been inactive for a specified period of time.

To enable the feature, return to your **All Devices** fleet, go to its **Settings**, and set an interval of your choosing. (During testing I recommend setting a short interval like one hour. You can always change the interval once you have things working.)

![Enabling watchdog events on a fleet](https://dev.blues.io/images/blog/posts/inactive-devices-smart-fleets/watchdog-events.png?v=8319b1c7)

If you have any already-inactive devices on your project you should see your first `_watchdog.qo` event appear for those devices within five minutes. After that, you’ll see one `_watchdog.qo` event each time your configured interval passes with no activity. For example, here’s the list of events I saw on my project after a few hours had passed.

![List of watchdog events](https://dev.blues.io/images/blog/posts/inactive-devices-smart-fleets/watchdog-events-list.png?v=0e6a8780)

## Step 3: Add Smart Fleet Rules

Your last step is to add [smart fleet rules](https://dev.blues.io/notehub/notehub-walkthrough.md#using-smart-fleet-rules) to your **Inactive** fleet. Smart fleet rules allow you to categorize devices based on event data, and you’ll use your newly enabled watchdog events to determine whether a device has been recently active or not.

To set this up, return to your **Inactive** fleet’s settings, add the following [JSONata expression](https://dev.blues.io/guides-and-tutorials/notecard-guides/using-jsonata-to-transform-json-in-notehub.md), and save.

```json
(file = "_watchdog.qo")
    ? $addToFleet() 
    : $removeFromFleet()
```

![Adding smart fleet rules](https://dev.blues.io/images/blog/posts/inactive-devices-smart-fleets/smart-fleet-rules.png?v=9b5e9cb9)

The code above is a JSONata expression that Notehub evaluates on each incoming event. The logic looks a bit complex, but it’s really doing one simple check: is the incoming event from the `_watchdog.qo` Notefile (does `file = "_watchdog.qo"`)?

- If `true`, that means the device is inactive (that’s the reason why it’s getting a `_watchdog.qo` event published), and that device should be **added** to the **Inactive** fleet (`$addToFleet()`).

- If `false`, that means Notehub received non-watchdog data from this device, which means it no longer inactive, and should be **removed** from the **Inactive** fleet (`removeFromFleet()`).

The great thing about smart fleets is that once you save these rules—you’re good to go! Notehub will continuously manage your fleet based off incoming data, and you’ll reliably have an up-to-date list of inactive devices to work with.

## Wrapping Up

In this article we looked at a workflow you can use to create a smart fleet of inactive devices on your Notehub projects.

What you do with this smart fleet is up to you.

For some, just having the list can be a nice way to spot check the health of their fleets at any time. For others, having automated reports can be a proactive way to investigate abnormal device behavior. For example, you could write a script that invokes the Notehub API’s [Get Fleet Devices](https://dev.blues.io/api-reference/notehub-api/device-api.md#get-fleet-devices) endpoint and emails you a list of your inactive devices daily.

Overall, with these Notehub features we aim to give you the tools you need to manage your fleets of devices easily, especially as your projects grow over time. If you have any feedback or suggestions, feel free to reach out in our [community forum](https://discuss.blues.com).