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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

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In order to run any of the following examples, you will first need to create a Function into which you can paste the example code. You can create a Function using the Twilio Console or the Serverless Toolkit as explained below:

ConsoleServerless Toolkit

If you prefer a UI-driven approach, creating and deploying a Function can be done entirely using the Twilio Console and the following steps:

  1. Log in to the Twilio Console and navigate to the Functions tab(link takes you to an external page) . If you need an account, you can sign up for a free Twilio account here(link takes you to an external page) !
  2. Functions are contained within Services . Create a Service by clicking the Create Service(link takes you to an external page) button and providing a name such as test-function .
  3. Once you've been redirected to the new Service, click the Add + button and select Add Function from the dropdown.
  4. This will create a new Protected Function for you with the option to rename it. The name of the file will be path it is accessed from.
  5. Copy any one of the example code snippets from this page that you want to experiment with, and paste the code into your newly created Function. You can quickly switch examples by using the dropdown menu of the code rail.
  6. Click Save to save your Function's contents.
  7. Click Deploy All to build and deploy the Function. After a short delay, your Function will be accessible from: https://<service-name>-<random-characters>-<optional-domain-suffix>.twil.io/<function-path>
    For example: test-function-3548.twil.io/hello-world .

Your Function is now ready to be invoked by HTTP requests, set as the webhook of a Twilio phone number, invoked by a Twilio Studio Run Function Widget, and more!


Respond to a call directly with TwiML

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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

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


Set a Function as a webhook

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In order for your Function to react to incoming SMS and/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, as detailed below:

Twilio ConsoleTwilio CLITwilio SDKs

You can use the Twilio Console(link takes you to an external page) UI as a straightforward way of connecting your Function as a webhook:

  1. Log in to the Twilio Console's Phone Numbers page(link takes you to an external page) .
  2. Click on the phone number you'd like to have connected to your Function.
  3. 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 .
  4. Select Function from the A Message Comes In or A Call Comes In dropdown.
  5. 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.
    Connect a Function as a Messaging webhook using the Function dropdowns.
  • Alternatively, you could select Webhook instead of Function, and directly paste in the full URL of the Function.
    Setting a Function as a Messaging webhook using the webhook dropdown option.
  1. Click the Save button.

Read out phone numbers in a Studio Flow

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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

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

Connect and configure your widgets

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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:

Studio Flow showing configuration for a Run Function widget that calls a phone number normalization Function.

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


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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

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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.

Normalize a phone number for the Say Widget

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Provides readable phone numbers to Studio Flows


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

Connect and test your Flow

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The last change necessary to test this out is to connect the Studio Flow to your Twilio phone number. You can follow these directions to do so.

With your Twilio phone number connected to the Studio Flow, you will now be able to call your Twilio phone number, and it will respond by reading out the number you are calling from in a human-friendly manner.


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