Receive an incoming phone call

When someone calls your Twilio number, Twilio can invoke a webhook that you've created to determine how to respond using TwiML. On this page, we will be providing some examples of Functions that can serve as the webhook of your Twilio number.

A Function that responds to webhook requests will receive details about the incoming phone call as properties on the event parameter. These include the phone number of the caller (event.From), the phone number of the recipient (event.To), and other relevant data such as geographic metadata about the phone numbers involved. You can view a full list of potential values at Twilio's request to your application.

Once a Function has been invoked on an incoming phone call, any number of actions can be taken. Below are some examples to inspire what you will build.

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.

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

Respond with a static message

For the most basic possible example, one can reply to the incoming phone call with a hardcoded message. To do so, you can create a new VoiceResponse and declare the intended message contents using the say method. Once your voice content has been set, you can return the generated TwiML by passing it to the callback function as shown and signaling a successful end to the function.

Respond to an incoming phone call

1exports.handler = (context, event, callback) => {
2  // Create a new voice response object
3  const twiml = new Twilio.twiml.VoiceResponse();
4  // Use any of the Node.js SDK methods, such as `say`, to compose a response
5  twiml.say('Ahoy, World!');
6  // Return the TwiML as the second argument to `callback`
7  // This will render the response as XML in reply to the webhook request
8  return callback(null, twiml);
9};

Respond dynamically to an incoming phone call

Because information about the incoming phone call is accessible from event object, it's also possible to tailor the response to the call based on that data. For example, you could respond with the city of the caller's phone number, or the number itself. The voice used to respond can also be modified, and pre-recorded audio can be used and/or added as well.

Read the in-depth <Say> documentation for more details about how to configure your response.

Respond dynamically to an incoming phone call

1exports.handler = (context, event, callback) => {
2  // Create a new voice response object
3  const twiml = new Twilio.twiml.VoiceResponse();
4  // Webhook information is accessible as properties of the `event` object
5  const city = event.FromCity;
6  const number = event.From;
7
8  // You can optionally edit the voice used, template variables into your
9  // response, play recorded audio, and more
10  twiml.say({ voice: 'alice' }, `Never gonna give you up, ${city || number}`);
11  twiml.play('https://demo.twilio.com/docs/classic.mp3');
12  // Return the TwiML as the second argument to `callback`
13  // This will render the response as XML in reply to the webhook request
14  return callback(null, twiml);
15};

Forward an incoming phone call

Another common use case is call forwarding. This could be handy in a situation where perhaps you don't want to share your real number while selling an item online, or as part of an IVR tree.

In this example, the Function will accept an incoming phone call and generate a new TwiML response that both notifies the user of the call forwarding and initiates a transfer of the call to the new number.

Read the in-depth <Dial>documentation for more details about connecting calls to other parties.

Forward an incoming phone call

1const NEW_NUMBER = "+15095550100";
2
3exports.handler = (context, event, callback) => {
4  // Create a new voice response object
5  const twiml = new Twilio.twiml.VoiceResponse();
6
7  twiml.say('Hello! Forwarding you to our new phone number now!');
8  // The `dial` method will forward the call to the provided E.164 phone number
9  twiml.dial(NEW_NUMBER);
10  // Return the TwiML as the second argument to `callback`
11  // This will render the response as XML in reply to the webhook request
12  return callback(null, twiml);
13};

(information)

Info

In this example, the number for call forwarding is hardcoded as a string in the Function for convenience. For a more secure approach, consider setting NEW_NUMBER as an Environment Variable in the Functions UI instead. It could then be referenced in your code as context.NEW_NUMBER, as shown in the following example.

Forward an incoming phone call

Use environment variables to store sensitive values

1exports.handler = (context, event, callback) => {
2  // Create a new voice response object
3  const twiml = new Twilio.twiml.VoiceResponse();
4  // Environment variables that you define can be accessed from `context`
5  const forwardTo = context.NEW_NUMBER;
6
7  twiml.say('Hello! Forwarding you to our new phone number now!');
8  // The `dial` method will forward the call to the provided E.164 phone number
9  twiml.dial(forwardTo);
10  // Return the TwiML as the second argument to `callback`
11  // This will render the response as XML in reply to the webhook request
12  return callback(null, twiml);
13};

Record an incoming phone call

Another common use case would be recording the caller's voice as an audio recording which can be retrieved later. Optionally, you can generate text transcriptions of recorded calls by setting the transcribe attribute of <Record> to true.

Read the in-depth <Record> documentation for more details about recording and/or transcribing calls.

Record an incoming phone call

1exports.handler = (context, event, callback) => {
2  // Create a new voice response object
3  const twiml = new Twilio.twiml.VoiceResponse();
4
5  twiml.say('Hello! Please leave a message after the beep.');
6  // Use <Record> to record the caller's message
7  twiml.record();
8  // End the call with <Hangup>
9  twiml.hangup();
10  // Return the TwiML as the second argument to `callback`
11  // This will render the response as XML in reply to the webhook request
12  return callback(null, twiml);
13};

Record and transcribe an incoming phone call

Use extra options to configure your recording

1exports.handler = (context, event, callback) => {
2  // Create a new voice response object
3  const twiml = new Twilio.twiml.VoiceResponse();
4
5  twiml.say('Hello! Please leave a message after the beep.');
6  // Use <Record> to record the caller's message.
7  // Provide options such as `transcribe` to enable message transcription.
8  twiml.record({ transcribe: true });
9  // End the call with <Hangup>
10  twiml.hangup();
11  // Return the TwiML as the second argument to `callback`
12  // This will render the response as XML in reply to the webhook request
13  return callback(null, twiml);
14};

Creating a moderated conference call

For something more exciting, Functions can also power conference calls. In this example, a "moderator" phone number of your choice will have control of the call in a couple of ways:

startConferenceOnEnter will keep all other callers on hold until the moderator joins
endConferenceOnExit will cause Twilio to end the call for everyone as soon as the moderator leaves

Incoming calls will be checked based on the incoming event.From value. If it matches the moderator's phone number, the call will begin and then end once the moderator leaves. Any other phone number will join normally and have no effect on the call's beginning or end.

Read the in-depth <Conference> documentation to learn more details.

Create a moderated conference call

1exports.handler = (context, event, callback) => {
2  // Create a new voice response object
3  const twiml = new Twilio.twiml.VoiceResponse();
4
5  // Start with a <Dial> verb
6  const dial = twiml.dial();
7  // If the caller is our MODERATOR, then start the conference when they
8  // join and end the conference when they leave
9  // The MODERATOR phone number MUST be in E.164 format such as "+15095550100"
10  if (event.From === context.MODERATOR) {
11    dial.conference('My conference', {
12      startConferenceOnEnter: true,
13      endConferenceOnExit: true,
14    });
15  } else {
16    // Otherwise have the caller join as a regular participant
17    dial.conference('My conference', {
18      startConferenceOnEnter: false,
19    });
20  }
21  // Return the TwiML as the second argument to `callback`
22  // This will render the response as XML in reply to the webhook request
23  return callback(null, twiml);
24};

Receive an incoming phone call

Create and host a Function

Run your Function in local development

Deploy your Function

Set a Function as a webhook

Respond with a static message

Respond to an incoming phone call

Respond dynamically to an incoming phone call

Respond dynamically to an incoming phone call

Forward an incoming phone call

Forward an incoming phone call

Info

Forward an incoming phone call

Record an incoming phone call

Record an incoming phone call

Record and transcribe an incoming phone call

Creating a moderated conference call

Create a moderated conference call