# User ID

{% hint style="info" %}
User ID is a unique identifier created for clients to distinguish users. 
{% endhint %}

To send messages based on the ID, proper integration is essential. When a user logs in, link the customer-managed user ID with the FlareLane device to distinguish between members and non-members.

## **Integrating User ID**

When a user successfully **logs in or registers**, assign a user ID so that the device can be identified using the customer’s user ID. Here's an example:

* [**Web SDK**](/guide-for-developers/web-sdk-reference.md) **/** [**Mobile SDK**](/guide-for-developers/mobile-sdk-reference.md): `FlareLane.setUserID("USER_ID")`

***

## **Checking User ID** 

Once the integration is complete, you can create groups to distinguish between members and non-members by using a filter in the segment that checks for the presence of a user ID.

<figure><img src="/files/Xp4w0FQvGSA9RZWLcLiP" alt="FlareLane All Devices page showing how to add User ID which identifies the customers as members or non-members"><figcaption><p><em>Image by FlareLane</em></p></figcaption></figure>

## Filtering Users

Using the user ID, you can segment your users into registered users and unregistered users, as shown below:

<figure><img src="/files/MkniunEAoNcJPPSCj5im" alt="FlareLane Segments page showing how to use User ID to create members and non-members segments"><figcaption><p>Image by FlareLane</p></figcaption></figure>


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