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

# Check Numbers

> Check which phone numbers are on WhatsApp.

## Overview

Tells which phone numbers have WhatsApp, from a connected **WhatsApp** account. Nothing is sent to them.

<Note>This endpoint consumes **1 credit** per call (up to 50 numbers). Ignore this if you're on per-seat pricing: usage is unlimited.</Note>

## Request

<ParamField header="x-api-key" type="string" required>
  Your API key for authentication.
</ParamField>

<ParamField body="account_id" type="string" required>
  A connected WhatsApp account.
</ParamField>

<ParamField body="action" type="string" required>
  Must be `"check_numbers"`.
</ParamField>

<ParamField body="params" type="object" required>
  <Expandable title="params properties">
    <ParamField body="phone_numbers" type="string[]" required>
      Up to 50 numbers in international format, e.g. `+33612345678`.
    </ParamField>
  </Expandable>
</ParamField>

```json Request theme={null}
{ "account_id": "your-whatsapp-account-id", "action": "check_numbers", "params": { "phone_numbers": ["+33612345678", "+33600000000"] } }
```

<ResponseExample>
  ```json 200 theme={null}
  {
    "success": true,
    "data": {
      "results": [
        { "phone_number": "+33612345678", "on_whatsapp": true, "conversation_id": "33612345678@s.whatsapp.net" },
        { "phone_number": "+33600000000", "on_whatsapp": false, "conversation_id": null }
      ],
      "total_results": 2
    },
    "metadata": { "action": "check_numbers", "account_id": "your-whatsapp-account-id", "credits_consumed": 1, "timestamp": "2026-09-26T15:40:00Z" }
  }
  ```

  ```json 400 theme={null}
  {
    "success": false,
    "error": { "code": "INVALID_PARAMS", "message": "At most 50 phone numbers per call" },
    "metadata": { "action": "check_numbers", "account_id": "your-whatsapp-account-id", "credits_consumed": 0, "timestamp": "2026-09-26T15:40:00Z" }
  }
  ```
</ResponseExample>