> ## 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.

# Set person properties

> Update user properties with setPersonProperties and setPersonPropertiesOnce

# Vue / Browser — Set person properties

Update user properties without changing the distinct ID. Use `setPersonProperties` to overwrite properties or `setPersonPropertiesOnce` to set them only if not already set.

## setPersonProperties(properties)

Sets or updates user properties (overwrites existing). Sends a `$set` event.

| Parameter    | Type                      | Required | Description                      |
| ------------ | ------------------------- | -------- | -------------------------------- |
| `properties` | `Record<string, unknown>` | yes      | User properties to set or update |

**When to use:** Update user properties after initial identification (e.g. plan changes, role updates, preference changes).

## setPersonPropertiesOnce(properties)

Sets user properties only if they are not already set. Sends a `$set_once` event.

| Parameter    | Type                      | Required | Description                                      |
| ------------ | ------------------------- | -------- | ------------------------------------------------ |
| `properties` | `Record<string, unknown>` | yes      | User properties to set (only if not already set) |

**When to use:** One-time attributes that shouldn't be overwritten (e.g. `signupSource`, `firstPurchaseDate`, `referralCode`).

## Vue example

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

let signal = null

onMounted(async () => {
  signal = createSignal({ endpoint: '...', apiKey: '...', projectId: '...' })
  await signal.start()
})

function updatePlan() {
  signal?.setPersonProperties({ plan: 'pro', role: 'admin' })
}

function setSignupSource() {
  // Only set if not already set
  signal?.setPersonPropertiesOnce({ signupSource: 'organic' })
}
</script>

<template>
  <div>
    <button @click="updatePlan">Upgrade Plan</button>
    <button @click="setSignupSource">Set Signup Source</button>
  </div>
</template>
```

## Vanilla JS example

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

// Update user plan
signal.setPersonProperties({ plan: 'enterprise', seats: 50 });

// Set signup source only if not already set
signal.setPersonPropertiesOnce({ signupSource: 'organic' });
```

## Differences from identify()

* **identify(distinctId, traits)** — Changes the user's distinct ID and sets properties. Use after login or when you know the user's identity.
* **setPersonProperties(properties)** — Updates properties without changing the distinct ID. Use when properties change after identification.
* **setPersonPropertiesOnce(properties)** — Sets properties only if not already set. Use for immutable attributes.

## See also

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