> ## Documentation Index
> Fetch the complete documentation index at: https://launchdarkly-preview.mintlify.site/llms.txt
> Use this file to discover all available pages before exploring further.

# Aliasing users

> This topic explains how to alias the users of various LaunchDarkly SDKs, both client- and server-side.

> For the complete documentation index, see [llms.txt](/llms.txt). For the full documentation snapshot, see [llms-full.txt](/llms-full.txt).

<Warning title="This feature is deprecated for SDKs that use contexts">
  LaunchDarkly no longer supports `alias` events for SDKs upgraded for contexts. LaunchDarkly continues to support sending and receiving alias events for older SDK versions. To learn more, read about our [SDKs that support contexts](/sdk).

  To learn how to associate contexts without using the `alias` method, read [Associate anonymous contexts with logged-in end users](/home/flags/anonymous-contexts#associate-anonymous-contexts-with-logged-in-end-users).
</Warning>

## Overview

This topic explains how to alias the users of various LaunchDarkly SDKs. This feature is available for both client-side and server-side SDKs, although its behavior differs between client-side and server-side SDKs.

## Aliased users

There are situations in which multiple LaunchDarkly users can represent one person. For example, this can happen when a person initially logs into an application. The person might be represented by an anonymous user before they log in, and a different user after they log in. In that case, that one person is identified by two different users as denoted by different user keys. Our SDKs can associate these two LaunchDarkly users by sending an `alias` event.

Only some LaunchDarkly SDKs offer the ability to manually send an `alias` event. Some client-side SDKs automatically send an `alias` event when identifying a known user if the previous user was anonymous. You can disable this behavior if necessary. To learn how, read [Configuration](/sdk/features/config).

Details about each SDK's configuration are available in the SDK-specific sections below:

* [Client-side SDKs](#client-side-sdks)
* [Server-side SDKs](#server-side-sdks)

## Client-side SDKs

This feature is no longer supported or required in any client-side SDKs. To learn more, read [Best practices for upgrading users to contexts](/guides/flags/upgrading-contexts), and consult the [custom contexts migration guide](/sdk) for each client-side SDK.

Older versions of these SDKs still support aliasing. Details for these older versions are included below.

### .NET (client-side)

In version 3 and newer of the .NET (client-side) SDK, aliasing is no longer supported or required. To learn more, read [.NET (client-side) SDK 2.x to 3.0 migration guide](/sdk/client-side/dotnet/migration-2-to-3).

<Accordion title="Expand .NET (client-side) code sample for older versions">
  To manually send an `alias` event:

  <CodeGroup>
    ```csharp title=".NET SDK 2.x (C#)" theme={null}
          client.Alias(newUser, previousUser);
    ```
  </CodeGroup>

  To learn more, read [`LdClient.Alias`](https://launchdarkly.github.io/dotnet-core/pkgs/sdk/client/api/LaunchDarkly.Sdk.Client.LdClient.html#LaunchDarkly_Sdk_Client_LdClient_Alias_) and [`ConfigurationBuilder.AutoAliasingOptOut`](https://launchdarkly.github.io/dotnet-core/pkgs/sdk/client/api/LaunchDarkly.Sdk.Client.LdClient.html#LaunchDarkly_Sdk_Client_ConfigurationBuilder_AutoAliasingOptOut_).
</Accordion>

### Android

In version 4.0 and newer of the Android SDK, aliasing is no longer supported or required. To learn more, read the [Android SDK 3.x to 4.0 migration guide](/sdk/client-side/android/migration-3-to-4).

<Accordion title="Expand Android code sample for older versions">
  To manually send an `alias` event:

  <CodeGroup>
    ```java title="Java" theme={null}
          client.alias(newUser, previousUser);
    ```

    ```kotlin title="Kotlin" theme={null}
          client.alias(newUser, previousUser)
    ```
  </CodeGroup>
</Accordion>

### C++ (client-side)

In version 3 and newer of the C++ (client-side) SDK, aliasing is no longer supported or required. To learn more, read [C++ (client-side) SDK 2.x to 3.0 migration guide](/sdk/client-side/c-c--/migration-2-to-3).

<Accordion title="Expand C/C++ (client-side) code sample for older versions">
  To manually send an `alias` event:

  <CodeGroup>
    ```c title="C SDK v2.0 (native)" theme={null}
          LDClientAlias(client, newUser, previousUser);
    ```
  </CodeGroup>
</Accordion>

### Electron

<Accordion title="Expand Electron code sample">
  To manually send an `alias` event:

  <CodeGroup>
    ```js title="JavaScript" theme={null}
          client.alias(newUser, previousUser);
    ```
  </CodeGroup>
</Accordion>

### Flutter

In version 2 and newer of the Flutter SDK, aliasing is no longer supported or required. To learn more, read the [Flutter SDK 1.x to 2.0 migration guide](/sdk/client-side/flutter/migration-1-to-2).

<Accordion title="Expand Flutter code sample for older versions">
  To manually send an `alias` event:

  <CodeGroup>
    ```dart title="Dart" theme={null}
          await LDClient.alias(newUser, previousUser);
    ```
  </CodeGroup>
</Accordion>

### iOS

In version 8 and newer of the iOS SDK, aliasing is no longer supported or required. To learn more, read the [iOS SDK 7.x to 8.0 migration guide for Objective-C](/sdk/client-side/ios/migration-7-to-8-objc) or for [Swift](/sdk/client-side/ios/migration-7-to-8-swift).

<Accordion title="Expand iOS code sample for older versions">
  To manually send an `alias` event:

  <CodeGroup>
    ```swift title="Swift" theme={null}
          LDClient.get()!.alias(context: newUser, previousContext: previousUser)
    ```

    ```objectivec title="Objective-C" theme={null}
          [[LDClient get] alias:newUser previousContext:previousUser];
    ```
  </CodeGroup>
</Accordion>

### Java

Script

In version 3 and newer of the JavaScript SDK, aliasing is no longer supported or required. To learn more, read [JavaScript SDK 2.x to 3.0 migration guide](/sdk/client-side/javascript/migration-2-to-3).

<Accordion title="Expand JavaScript code sample for older versions">
  Both `alias` parameters must have `key` attributes. If the LaunchDarkly client auto-generated a unique identifier for one of your users, you can access the user's complete object with the `getUser` method.

  To manually send an `alias` event:

  <CodeGroup>
    ```js title="JavaScript SDK v2.x" theme={null}
          const previousUser = client.getUser();
          client.alias(newUser, previousUser);
    ```
  </CodeGroup>
</Accordion>

### Node.js (client-side)

In version 3 and newer of the Node.js SDK, aliasing is no longer supported or required. To learn more, read [Node.js (client-side) SDK 2.x to 3.0 migration guide](/sdk/client-side/node-js/migration-2-to-3).

<Accordion title="Expand Node.js (client-side) code sample for older versions">
  To manually send an `alias` event:

  <CodeGroup>
    ```js title="JavaScript" theme={null}
          client.alias(newUser, previousUser);
    ```
  </CodeGroup>
</Accordion>

### React Native

In version 7 and newer of the React Native SDK, aliasing is no longer supported or required. To learn more, read [React Native SDK 6.x to 7.0 migration guide](/sdk/client-side/react/migration-6-to-7-react-native).

<Accordion title="Expand React Native code sample for older versions">
  To manually send an `alias` event:

  <CodeGroup>
    ```js title="JavaScript" theme={null}
          client.alias(user, previousUser);

          // to send an alias event in a different environment than the default,
          // pass in the environment key (optional)
          client.alias(user, previousUser, environment);
    ```
  </CodeGroup>
</Accordion>

### Roku

In version 2 and newer of the Roku SDK, aliasing is no longer supported or required. To learn more, read [Roku SDK 1.x to 2.0 migration guide](/sdk/client-side/roku/migration-1-to-2).

<Accordion title="Expand Roku code sample for older versions">
  To manually send an `alias` event:

  <CodeGroup>
    ```brightscript title="BrightScript" theme={null}
          client.alias(user, previousUser)
    ```
  </CodeGroup>
</Accordion>

## Server-side SDKs

This feature is available in the following server-side SDKs:

* [Apex](#apex)

### .NET (server-side)

In version 7.0 and newer of the .NET (server-side) SDK, aliasing is no longer supported or required. To learn more, read [.NET (server-side) SDK 6.x to 7.0 migration guide](/sdk/server-side/dotnet/migration-6-to-7).

<Accordion title="Expand .NET (server-side) code sample for older versions">
  To manually send an `alias` event:

  <CodeGroup>
    ```csharp title=".NET SDK v7.0 and earlier (C#)" theme={null}
          client.Alias(newUser, previousUser);
    ```
  </CodeGroup>
</Accordion>

### Apex

<Accordion title="Expand Apex code sample">
  To manually send an `alias` event:

  <CodeGroup>
    ```java title="Apex" theme={null}
          client.alias(newUser, previousUser)
    ```
  </CodeGroup>
</Accordion>

### C++ (server-side)

In version 3.0 and newer of the C++ (server-side) SDK, aliasing is no longer supported or required. To learn more, read [C++ (server-side) SDK 2.x to 3.0 migration guide](/sdk/server-side/c-c--/migration-2-to-3).

<Accordion title="Expand C++ (server-side) code sample for older versions">
  To manually send an `alias` event:

  <CodeGroup>
    ```c title="C/C++" theme={null}
          LDClientAlias(client, newUser, previousUser);
    ```
  </CodeGroup>
</Accordion>

### Erlang

In version 2 and newer of the Erlang SDK, aliasing is no longer supported or required. To learn more, read [Erlang SDK 1.x to 2.0 migration guide](/sdk/server-side/erlang/migration-1-to-2).

<Accordion title="Expand Erlang code sample for older versions">
  To manually send an `alias` event:

  <CodeGroup>
    ```erlang title="Erlang" theme={null}
          ldclient:alias(User, PreviousUser)
    ```
  </CodeGroup>
</Accordion>

### Go

In version 6.0 and newer of the Go SDK, aliasing is no longer supported or required. To learn more, read [Go SDK 5.x to 6.0 migration guide](/sdk/server-side/go/migration-5-to-6).

<Accordion title="Expand Go code sample for older versions">
  To manually send an `alias` event in older versions of the Go SDK:

  <CodeGroup>
    ```go title="Go SDK v5.x and earlier" theme={null}
          client.Alias(newUser, previousUser)
    ```
  </CodeGroup>
</Accordion>

### Haskell

In version 4 and newer of the Haskell SDK, aliasing is no longer supported or required. To learn more, read [Haskell SDK 3.x to 4.0 migration guide](/sdk/server-side/haskell/migration-3-to-4).

<Accordion title="Expand Haskell code sample for older versions">
  To manually send an `alias` event:

  <CodeGroup>
    ```haskell title="Haskell" theme={null}
          alias client newUser previousUser
    ```
  </CodeGroup>
</Accordion>

### Java

In version 6 and newer of the Java SDK, aliasing is no longer supported or required. To learn more, read [Java SDK 5.x to 6.0 migration guide](/sdk/server-side/java/migration-5-to-6).

<Accordion title="Expand Java code sample for older versions">
  To manually send an `alias` event:

  <CodeGroup>
    ```java title="Java SDK v5.x and earlier" theme={null}
          client.alias(user, previousUser);
    ```
  </CodeGroup>
</Accordion>

### Lua

In version 2.0 and newer of the Lua SDK, aliasing is no longer supported or required. To learn more, read [Lua (server-side) SDK 1.x to 2.0 migration guide](/sdk/server-side/lua/migration-1-to-2).

<Accordion title="Expand Lua code sample for older versions">
  To manually send an `alias` event:

  <CodeGroup>
    ```lua title="Lua SDK v1.x" theme={null}
          client:alias(newUser, previousUser)
    ```
  </CodeGroup>
</Accordion>

### Node.js (server-side)

In version 7.0 and newer of the Node.js (server-side) SDK, aliasing is no longer supported or required. To learn more, read [Node.js (server-side) SDK 6.x to 7.0 migration guide](/sdk/server-side/node-js/migration-6-to-7).

<Accordion title="Expand Node.js (server-side) code sample for older versions">
  To manually send an `alias` event:

  <CodeGroup>
    ```js title="JavaScript" theme={null}
          client.alias(newUser, previousUser);
    ```
  </CodeGroup>
</Accordion>

### PHP

In version 5.0 and newer of the PHP SDK, aliasing is no longer supported or required. To learn more, read [PHP SDK 4.x to 5.0 migration guide](/sdk/server-side/php/migration-4-to-5).

<Accordion title="Expand PHP code sample for older versions">
  To manually send an `alias` event:

  <CodeGroup>
    ```php title="PHP" theme={null}
          $client->alias($user, $previousUser);
    ```
  </CodeGroup>
</Accordion>

### Python

In version 8 and newer of the Python SDK, aliasing is no longer supported or required. To learn more, read [Python SDK 7.x to 8.0 migration guide](/sdk/server-side/python/migration-7-to-8).

<Accordion title="Expand Python code sample for older versions">
  To manually send an `alias` event:

  <CodeGroup>
    ```python title="Python SDK v7.x and earlier" theme={null}
          ldclient.get().alias(new_user, previous_user)
    ```
  </CodeGroup>
</Accordion>

### Ruby

In version 7 and newer of the Ruby SDK, aliasing is no longer supported or required. To learn more, read [Ruby SDK 6.x to 7.0 migration guide](/sdk/server-side/ruby/migration-6-to-7).

<Accordion title="Expand Ruby code sample for older versions">
  To manually send an `alias` event:

  <CodeGroup>
    ```ruby title="Ruby SDK v6.x and earlier" theme={null}
          client.alias(new_user, previous_user)
    ```
  </CodeGroup>
</Accordion>

### Rust

In version 1 and newer of the Rust SDK, aliasing is not supported or required. To learn more, read [Rust SDK v1 implementation guide](/sdk/server-side/rust/implementation-v1).

<Accordion title="Expand Rust code sample for the beta version">
  To manually send an `alias` event:

  <CodeGroup>
    ```rust title="Rust" theme={null}
          client.alias(user, previous_user);
    ```
  </CodeGroup>
</Accordion>