# Determine carrier, phone number type, and caller info

[Twilio Lookup](/docs/lookup) allows you to get information about phone numbers programmatically. This information can include the name of the phone number's carrier, their type (landline, mobile, VoIP, etc.), the name of the caller, and far more than this example page can cover.

All this data can be indispensable in making your applications dynamic and able to handle different carriers. The following examples illustrate a small sample of what Lookup can enable in Twilio Functions, and we can't wait to see what else you will build.

To get started, use the following instructions to create a Function to host your code.

## Create and host a Function

Before you run any of the examples on this page, create a Function and paste the example code into it. You can create a Function in the Twilio Console or by using the [Serverless Toolkit](/docs/labs/serverless-toolkit).

## Console

If you prefer a UI-driven approach, complete these steps in the Twilio Console:

1. Log in to the [Twilio Console](https://1console.twilio.com) and navigate to **Develop > Functions & Assets**. If you're using the *legacy* Console, open the [**Functions** tab](https://www.twilio.com/console/functions/overview).
2. Functions are contained within **Services**. Click **[Create Service](https://www.twilio.com/console/functions/overview/services)** to create a new **[Service](/docs/serverless/functions-assets/functions/create-service)**.
3. Click **Add +** and select **Add Function** from the dropdown.
4. The Console creates a new [protected](/docs/serverless/functions-assets/visibility) Function that you can rename. The filename becomes the URL path of the Function.
5. Copy one of the example code snippets from this page and paste the code into your newly created Function. You can switch examples by using the dropdown menu in the code rail.
6. Click **Save**.
7. Click **Deploy All** to build and deploy the Function. After deployment, you can access your Function at `https://<service-name>-<random-characters>-<optional-domain-suffix>.twil.io/<function-path>`\
   For example: `test-function-3548.twil.io/hello-world`.

## Serverless Toolkit

The [Serverless Toolkit](/docs/labs/serverless-toolkit) lets you develop locally, deploy projects, and perform other tasks through the [Twilio CLI](/docs/twilio-cli/quickstart).

1. From the CLI, run `twilio serverless:init <YOUR-SERVICE-NAME> --empty` to bootstrap your local environment.
2. Go to your new project directory using `cd <YOUR-SERVICE-NAME>`.
3. In the `/functions` directory, create a JavaScript file whose name reflects the purpose of the Function. For example, `sms-reply.protected.js` for a [protected](/docs/serverless/functions-assets/visibility) Function intended to handle incoming SMS.
4. Add the code example of your choice to the file and save it. Note that a Function can only export a single handler. You need to create separate files to run or deploy multiple examples at once.

After you save the Function code, you can test it locally (and optionally tunnel requests to it using a tool like [ngrok](https://ngrok.com/)), or deploy it.

### Run your Function in local development

Run `twilio serverless:start` from your CLI to start the project locally. The Function(s) in your project are accessible from `http://localhost:3000/sms-reply`

* If you want to test a Function as a [Twilio webhook](/docs/usage/webhooks/getting-started-twilio-webhooks), run: `twilio phone-numbers:update <your Twilio phone number> --sms-url "http://localhost:3000/sms-reply"`\
  This automatically generates an ngrok tunnel from Twilio to your locally running Function, so you can start sending texts to it. You can apply the same process but with the `voice-url` flag instead to test with [Twilio Voice](/docs/voice).
* If your code does *not* connect to Twilio Voice or Messages as a webhook, start your dev server and start an ngrok tunnel in the same command with the `ngrok` flag. For example: `twilio serverless:start --ngrok=""`

### Deploy your Function

To deploy your Function and have access to live url(s), run `twilio serverless:deploy` from your CLI. This deploys your Function(s) to Twilio under a development Environment by default, where they can be accessed from:

`https://<service-name>-<random-characters>-dev.twil.io/<function-path>`

For example: `https://incoming-sms-examples-3421-dev.twil.io/sms-reply`

You can now invoke your Function with HTTP requests, configure it as the [webhook](/docs/usage/webhooks/getting-started-twilio-webhooks) for a Twilio phone number, call it from a Twilio Studio [**Run Function** Widget](/docs/studio/widget-library/run-function), and more.

## Identify a phone number's carrier and type

The core functionality of Lookup is determining the carrier and type of a phone number. For example, the following Function code returns true for incoming calls from landline or mobile callers, and false for calls from VoIP callers. An application could use this information to filter out unsupported call types in a Studio Flow if called by a [Run Function widget](/docs/serverless/functions-assets/quickstart/run-function-studio-widget), or simply called as a REST API by your application.

```js title="Lookup with an E.164 Formatted Number"
exports.handler = async (context, event, callback) => {
  // The pre-initialized Twilio client is available from the `context` object
  const client = context.getTwilioClient();

  // Grab the incoming phone number from a call/message webhook via event.From
  // If invoked by a REST API call or Studio Run Function widget, it may be a
  // parameter such as phoneNumber
  // Example: https://x.x.x.x/<path>?phoneNumber=%2b15105550100
  const phoneNumber = event.From || event.phoneNumber || '+15105550100';

  try {
    // Discover the phone number's carrier and type using the Lookup API with
    // the `type: 'carrier'` argument
    const result = await client.lookups
      .phoneNumbers(phoneNumber)
      .fetch({ type: 'carrier' });

    console.log('Carrier name: ', result.carrier.name);
    // 'Carrier name: AT&T'
    console.log('Carrier type: ', result.carrier.type);
    // 'Carrier type: mobile'

    // Reject calls from VoIP numbers, and allow all others
    return callback(null, result.carrier.type !== 'voip');
  } catch (error) {
    console.error(error);
    return callback(error, null);
  }
};
```

## Get a name associated with a phone number

Lookup can also retrieve the name of the individual or business associated with a phone number. Expanding on the previous example, convert the `type` argument to an array, and add `'caller-name'` after `'carrier'`.

If available, the response will include a name for the phone number and whether the name is for a `business` or `consumer`.

> \[!WARNING]
>
> Keep in mind that not all numbers will have names available.

You can then use this information to adjust application logic, format responses to use names to add personalization, and more.

For this example, the code attempts to format the caller's name and use it in a response, falling back to referencing the carrier name if the caller's name isn't accessible. To test this code out, paste the code into your existing Function, and set it as the **A Call Comes In** webhook handler for the Twilio phone number you wish to test. The following instructions will show you how to do so.

```js title="Lookup caller name and type"
// !mark(19,25,26,27,28,30,31,32,33,34,35,36)
// lodash is a default dependency for deployed Functions, so it can be imported
// with no changes on your end
const { startCase } = require('lodash');

exports.handler = async (context, event, callback) => {
  // The pre-initialized Twilio client is available from the `context` object
  const client = context.getTwilioClient();

  // Grab the incoming phone number from a call webhook via event.From
  const phoneNumber = event.From;

  try {
    // Create a new voice response object
    const twiml = new Twilio.twiml.VoiceResponse();
    // Discover the phone number's name (if possible) by converting type
    // to an array and appending 'caller-name' to the type argument
    const result = await client.lookups
      .phoneNumbers(phoneNumber)
      .fetch({ type: ['carrier', 'caller-name'] });

    console.log('Carrier name: ', result.carrier.name);
    // 'Carrier name: AT&T'
    console.log('Carrier type: ', result.carrier.type);
    // 'Carrier type: mobile'
    console.log('Caller name: ', result.callerName.caller_name);
    // 'Caller name: DOE,JOHN'
    console.log('Caller type: ', result.callerName.caller_type);
    // Caller type: CONSUMER'

    if (result.callerName.caller_name) {
      // Attempt to nicely format the users name in a response, if it exists
      const [lastName, firstName] = result.callerName.caller_name
        .toLowerCase()
        .split(',');
      const properName = startCase(`${firstName} ${lastName}`);
      twiml.say(`Great to hear from you, ${properName}!`);
    } else {
      // If we don't have a name, fallback to reference the carrier instead
      twiml.say(`We love hearing from ${result.carrier.name} customers!`);
    }

    return callback(null, twiml);
  } catch (error) {
    console.error(error);
    return callback(error, null);
  }
};
```

## Set a Function as a webhook

For your Function to react to incoming SMS or voice calls, it must be set as a [webhook](/docs/usage/webhooks) for your Twilio number. There are a variety of methods to set a Function as a webhook:

![Setting a Function as a Messaging webhook using the webhook dropdown option.](https://docs-resources.prod.twilio.com/bf4eae4ac40fe7d47003a93bca295d5c232e0b372358e73ceff931fee3ccdc4f.png)