> ## Documentation Index
> Fetch the complete documentation index at: https://docs.trysignal.ai/llms.txt
> Use this file to discover all available pages before exploring further.

# Alias

> Link an alias to a user with signal.alias()

# Vue / Browser — Alias

Link an alias (e.g. anonymous ID) to the current user. Use this to merge anonymous events (from before login) with the identified user.

## alias(alias)

Links an alias to the current user. Sends a `$create_alias` event.

| Parameter | Type     | Required | Description                                |
| --------- | -------- | -------- | ------------------------------------------ |
| `alias`   | `string` | yes      | Alias to link (e.g. previous anonymous ID) |

**When to use:** After login to merge anonymous events (from before login) with the identified user. This ensures all events are associated with the same user profile.

## Vue example

```vue theme={null}
<script setup>
import { onMounted, ref } from 'vue'
import { createSignal } from '@signal-js/browser'

let signal = null
const anonymousId = ref(null)

onMounted(async () => {
  signal = createSignal({ endpoint: '...', apiKey: '...', projectId: '...' })
  await signal.start()
  
  // Store anonymous ID before login
  const stored = localStorage.getItem('anonymous_id')
  if (stored) {
    anonymousId.value = stored
  }
})

function handleLogin(userId, userTraits) {
  // Identify the user
  signal?.identify(userId, userTraits)
  
  // Link anonymous ID if it exists
  if (anonymousId.value) {
    signal?.alias(anonymousId.value)
    localStorage.removeItem('anonymous_id')
  }
}
</script>

<template>
  <button @click="handleLogin('user_123', { email: 'user@example.com' })">
    Log in
  </button>
</template>
```

## Vanilla JS example

```javascript theme={null}
const signal = createSignal({ endpoint: '...', apiKey: '...', projectId: '...' });
await signal.start();

// Store anonymous ID before login
let anonymousId = localStorage.getItem('anonymous_id') || null;

function handleLogin(userId, userTraits) {
  // Identify the user
  signal.identify(userId, userTraits);
  
  // Link anonymous ID if it exists
  if (anonymousId) {
    signal.alias(anonymousId);
    localStorage.removeItem('anonymous_id');
  }
}
```

## How it works

1. **Before login:** User browses anonymously. Events are tracked with an anonymous ID.
2. **After login:** Call `identify(userId, traits)` to set the user's identity.
3. **Link alias:** Call `alias(anonymousId)` to link the anonymous ID to the identified user.
4. **Result:** All events (both anonymous and identified) are now associated with the same user profile.

## See also

* [Identify](/docs/integrations/vue/identify) — identify() and reset()
* [Capture](/docs/integrations/vue/capture) — Track events