Normalize telephone numbers

Twilio's APIs consistently use the E.164 standard for phone numbers. This format is fine within your code, but it presents a couple of user-facing issues:

E.164 is difficult to understand when presented as plain text, such as in an SMS
When read aloud by a Twilio Say verb or Say Widget, numbers such as +15095550100 will be read literally as a large number, instead of digit-by-digit. (ex. "Plus fifteen billion, ninety-five million, five hundred fifty thousand, one hundred")

Fortunately, Twilio Lookup enables you to convert a given E.164 phone number into the national format used by that country, which Twilio will read aloud as one would normally say it in their region.

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.

ConsoleServerless Toolkit

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

Log in to the Twilio Console and navigate to Develop > Functions & Assets. If you're using the legacy Console, open the Functions tab.
Functions are contained within Services. Click Create Service to create a new Service.
Click Add + and select Add Function from the dropdown.
The Console creates a new protected Function that you can rename. The filename becomes the URL path of the Function.
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.
Click Save.
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.

You can now invoke your Function with HTTP requests, configure it as the webhook for a Twilio phone number, call it from a Twilio Studio Run Function Widget, and more.

Respond to a call directly with TwiML

The following Function is one which will tell the user their phone number, in the format that they would expect in normal conversation. This will also work for international phone numbers!

To verify this for yourself, paste the code into the Function that you just made, 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.

Convert a number to its national format

1exports.handler = async (context, event, callback) => {
2  // The pre-initialized Twilio client is available from the `context` object
3  const client = context.getTwilioClient();
4  // Create a new voice response object
5  const twiml = new Twilio.twiml.VoiceResponse();
6
7  // The From value is provided by Twilio to this webhook Function, and contains the caller's
8  // phone number in E.164 format, ex. '+15095550100'
9  const from = event.From;
10
11  // Call Twilio Lookup to get information about the number, including its national format
12  const result = await client.lookups.phoneNumbers(from).fetch();
13
14  // Read back the caller's phone number in the way it would normally spoken, not as a
15  // massive integer!
16  twiml.say(`Your phone number is ${result.nationalFormat}`);
17  return callback(null, twiml);
18};

Set a Function as a webhook

For your Function to react to incoming SMS or voice calls, it must be set as a webhook for your Twilio number. There are a variety of methods to set a Function as a webhook:

Twilio ConsoleLegacy Twilio ConsoleTwilio CLITwilio server-side SDKs

Use the Twilio Console UI to connect your Function as a webhook:

Go to Products & Services > Numbers & Senders > Phone Numbers.
Select the phone number you'd like to connect to your Function.
Go to the Configuration Details tab.

To configure Messaging, choose Edit details in the Messaging section.
To configure Voice calls, choose Edit details in the Voice and emergency calling section.

Select the webhook method and provide your webhook URL. Select an HTTP method to handle responses.
Optional: Configure a secondary webhook in case the primary webhook fails.
Click the Save button.

In the legacy Twilio Console, connect your Function as a webhook:

Log in to the Twilio Console's Phone Numbers page.
Click on the phone number you'd like to have connected to your Function.
If you want the Function to respond to incoming SMS, find the A Message Comes In option under Messaging. If you want the Function to respond to Voice, find the A Call Comes In option under Voice & Fax.
Select Function from the A Message Comes In or A Call Comes In dropdown.
Select the Service that you are using, then the Environment (this will default to ui unless you have created custom domains ), and finally Function Path of your Function from the respective dropdown menus.

Alternatively, you could select Webhook instead of Function, and directly paste in the full URL of the Function.

Click the Save button.

You can also use the Twilio CLI to assign the Function as the webhook of your phone number.

Prerequisites

Twilio CLI installed and executable from your terminal.
Either the E.164 formatted value of your Twilio phone number (+1234567890), or its SID (PNXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX).
The full URL of your Function (https://test-1337.twil.io/my-test-function)

Once you have the CLI installed and the necessary information, run the following to connect the Function to respond to incoming SMS:

1twilio phone-numbers:update +1234567890 \
2  --sms-url https://test-1337.twil.io/my-test-function

If you prefer to have the Function respond to incoming calls instead, run:

1twilio phone-numbers:update +1234567890 \
2  --voice-url https://test-1337.twil.io/my-test-function

You may also use the SID of your Twilio phone number instead of the E.164 formatted phone number:

1twilio phone-numbers:update PNXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX \
2  --sms-url https://test-1337.twil.io/my-test-function

You can also use any of the available Twilio SDKs to assign the Function as the webhook of your phone number.

Prerequisites

A local development environment for your language of choice and the associated Twilio SDK installed.
The SID (PNXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX) of your Twilio phone number.
The full URL of your Function (https://test-1337.twil.io/my-test-function).

In JavaScript for example, you could execute the following code to assign the SMS webhook of your Twilio phone number. The same logic would apply for assigning to a voice webhook, except that the modified property instead would be voiceUrl:

1// Download the SDK from https://www.twilio.com/docs/node/install
2// Find your Account SID and Auth Token at twilio.com/console
3// and set the environment variables. See https://twil.io/secure
4const accountSid = process.env.TWILIO_ACCOUNT_SID;
5const authToken = process.env.TWILIO_AUTH_TOKEN;
6const client = require('twilio')(accountSid, authToken);
7
8client
9  .incomingPhoneNumbers('PNXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX')
10  .update({ smsUrl: 'https://test-1337.twil.io/my-test-function' })
11  .then((phoneNumber) => console.log(phoneNumber.smsUrl));
12

Read out phone numbers in a Studio Flow

This functionality also lends itself well to Studio Flows, where you may share a phone number as part of your IVR. The Say widget doesn't natively read E.164 formatted numbers in the national format, but clever use of the Run Function widget with the following sample code will enable this.

Create a Studio Flow

First, create a new Studio Flow. We suggest following the Create Your Flow directions from a Studio tutorial.

Connect and configure your widgets

Once you have created a Flow, drag a Run Function and a Say/Play widget onto the Studio canvas. Connect the Incoming Call trigger to the Run Function widget by dragging from the trigger to on top of the widget, and similarly connect the Run Function widget's "Success" condition to the Say/Play widget.

With the widgets connected, the next step is to configure them.

Click on the Run Function widget, which should cause the Widget Library to show the configuration options for the widget. Name the widget as you like, and use the drop-down menus to select the Service and path of the Function that you created previously. To wrap up the configuration, click Add under Function Parameters, set the "Key" to From, and "Value" to {{contact.channel.address}}. This will cause the phone number of the incoming caller to be passed to the Function as a parameter called From.

Your configuration and connections should look similar to this:

Twilio Studio Flow with Run Function widget for phone number formatting.

Following a similar process, configure the Say/Play widget with your desired name, and paste the following into the "Text to Say" field:

Hi! Your phone number is {{widgets.<widget-name>.parsed.normalizedPhoneNumber}}.

Replace <widget-name> with the name of your Run Function widget. This means the Say/Play widget will access the results of the Run Function widget, retrieve a value named normalizedPhoneNumber, and will attempt to read it back to the caller. You can read here to get more context around the parsed property.

Click Publish to publish your Studio Flow.

Update your Function's code

With the Studio Flow published and expecting new behavior from your Function, it will need some slight modifications.

Edit or replace the body of your Function with the following sample code. Note that it is returning the normalizedPhoneNumber that is expected by the Say/Play widget.

With your code changes complete, save and deploy your Function.

Provides readable phone numbers to Studio Flows

1exports.handler = async (context, event, callback) => {
2  // The pre-initialized Twilio client is available from the `context` object
3  const client = context.getTwilioClient();
4  // The From value should be provided as a parameter by the Run Function widget, and contains
5  // the caller's phone number in E.164 format, ex. '+15095550100'
6  const from = event.From;
7
8  // Call Twilio Lookup to get information about the number, including its national format
9  const result = await client.lookups.phoneNumbers(from).fetch();
10
11  // Return the caller's phone number in the way it would normally spoken
12  // Access this in a Studio Flow with `{{widgets.<widget-name>.parsed.normalizedPhoneNumber}}`
13  return callback(null, {
14    normalizedPhoneNumber: result.nationalFormat,
15  });
16};

Connect and test your Flow

To test your Flow, connect your Twilio phone number to the Studio Flow.

With your Twilio phone number connected to the Studio Flow, you can call your Twilio phone number and have a synthesized voice read out the number you are calling from in a human-friendly manner.