---
updatedAt: 2026-06-11T13:39:34.000Z
agentTools:
  projectIndex: https://developers.wingify.com/v2/llms.txt
---

# User ID

You can identify a user in the Wingify SDK using a string which identifies that user.\
User Id can be set in the Wingify Launch config.

User Id helps Wingify identify a user across multiple devices, it allows us to serve the same variation to a user thus keeping the experience consistent.

For example, you may run a campaign on both iPhone and iPad. If a user uses both the iPhone app and iPad app, setting the user id will allow us to serve the same variation for a campaign.

```java
String id = "<uuid-for-the-user>";
VWOConfig vwoConfig = new VWOConfig.Builder().userID(id).build();

VWO.with(this, VWO_API_KEY).config(vwoConfig).launch(null);
```
```kotlin
val id = "<uuid-for-the-user>"
val vwoConfig = VWOConfig.Builder().userID(id).build()

VWO.with(this, VWO_API_KEY).config(vwoConfig).launch(null)
```

Please note that altering the traffic allocation among variations or total campaign traffic can break this. Also, changing targetting while the campaign is running is also not advisable.

> 📘 Please note
>
> User ID is used as hash and is not stored anywhere on the device or server.