A Call is an object that represents a connection between a telephone and Twilio.
Using this resource, you can initiate a call, fetch information about a completed call, fetch a list of calls made to and from your account, redirect or end a call that is in progress, and delete records of past calls from your account.
An inbound call occurs when a person calls one of your Twilio phone numbers, client connections, or SIP-enabled endpoints. An outbound call happens when you initiate a call from a Twilio phone number to an outside phone number, client, or SIP domain.
You can initiate an outbound call by sending an HTTP POST request to the Call resource. Calls are rate limited at the account level by Calls Per Second (CPS). Calls beyond your account's CPS limit will be queued and will execute at the CPS rate.
The queue_time parameter provides an estimate for how long before the call is executed. You can reduce queue_time by increasing the CPS value on your account.
(information)
Calls Per Second (CPS)
By default, each account is granted one CPS for calls created via POST requests to the /Calls endpoint. Inbound calls and <Dial> calls are not limited by CPS.
Accounts with an approved Business Profile can update their CPS up to 30 in the Twilio Console.
In aggregate, calls are executed at the rate defined by the CPS. Individual calls may not execute at the anticipated rate — you may see individual seconds with more or fewer CPS, especially for inconsistent traffic — but over a month, the call execution rate will average the CPS rate set for that account or trunk.
You can also initiate a call from an active call (e.g., forwarding to another number or dialing into a conference) by including TwiML's <Dial> verb in your TwiML application. However, the only way to initiate a call directly from Twilio is with an API request.
(information)
Info
Are you looking for step-by-step instructions for making your first call with Twilio using the helper libraries? Check out one of our quickstarts in your programming language of choice: C#/.NET, Java, Node.js, PHP, Python, or Ruby.
The phone number, SIP address, Client identifier or SIM SID that received this call. Phone numbers are in E.164 format (e.g., +16175551212). SIP addresses are formatted as name@company.com. Client identifiers are formatted client:name. SIM SIDs are formatted as sim:sid.
The phone number, SIP address or Client identifier that received this call. Formatted for display. Non-North American phone numbers are in E.164 format (e.g., +442071838750).
The phone number, SIP address, Client identifier or SIM SID that made this call. Phone numbers are in E.164 format (e.g., +16175551212). SIP addresses are formatted as name@company.com. Client identifiers are formatted client:name. SIM SIDs are formatted as sim:sid.
The calling phone number, SIP address, or Client identifier formatted for display. Non-North American phone numbers are in E.164 format (e.g., +442071838750).
If the call was inbound, this is the SID of the IncomingPhoneNumber resource that received the call. If the call was outbound, it is the SID of the OutgoingCallerId resource from which the call was placed.
The status of this call. Can be: queued, ringing, in-progress, canceled, completed, failed, busy or no-answer. See Call Status Values below for more information.
The charge for this call, in the currency associated with the account. Populated after the call is completed. May not be immediately available. The price associated with a call only reflects the charge for connectivity. Charges for other call-related features such as Answering Machine Detection, Text-To-Speech, and SIP REFER are not included in this value.
A string describing the direction of the call. Can be: inbound for inbound calls, outbound-api for calls initiated via the REST API or outbound-dial for calls initiated by a <Dial> verb. Using Elastic SIP Trunking, the values can be trunking-terminating for outgoing calls from your communications infrastructure to the PSTN or trunking-originating for incoming calls to your communications infrastructure from the PSTN.
The forwarding phone number if this call was an incoming call forwarded from another number (depends on carrier supporting forwarding). Otherwise, empty.
The unique identifier of the trunk resource that was used for this call. The field is empty if the call was not made using a SIP trunk or if the call is not terminated.
The call could not be completed as dialed, most likely because the provided number was invalid.
Create a Call resource
POST https://api.twilio.com/2010-04-01/Accounts/{AccountSid}/Calls.json
Calls can be made via the REST API to phone numbers, SIP addresses, or client identifiers. To place a new outbound call, make an HTTP POST request to your account's Call resource.
The phone number or client identifier to use as the caller id. If using a phone number, it must be a Twilio number or a Verified outgoing caller id for your account. If the to parameter is a phone number, From must also be a phone number.
The HTTP method we should use when calling the url parameter's value. Can be: GET or POST and the default is POST. If an application_sid parameter is present, this parameter is ignored.
The URL that we call using the fallback_method if an error occurs when requesting or executing the TwiML at url. If an application_sid parameter is present, this parameter is ignored.
The HTTP method that we should use to request the fallback_url. Can be: GET or POST and the default is POST. If an application_sid parameter is present, this parameter is ignored.
The URL we should call using the status_callback_method to send status information to your application. If no status_callback_event is specified, we will send the completed status. If an application_sid parameter is present, this parameter is ignored. URLs must contain a valid hostname (underscores are not permitted).
The call progress events that we will send to the status_callback URL. Can be: initiated, ringing, answered, and completed. If no event is specified, we send the completed status. If you want to receive multiple events, specify each one in a separate status_callback_event parameter. See the code sample for monitoring call progress. If an application_sid is present, this parameter is ignored.
The HTTP method we should use when calling the status_callback URL. Can be: GET or POST and the default is POST. If an application_sid parameter is present, this parameter is ignored.
A string of keys to dial after connecting to the number, maximum of 32 digits. Valid digits in the string include: any digit (0-9), '#', '*' and 'w', to insert a half second pause. For example, if you connected to a company phone number and wanted to pause for one second, and then dial extension 1234 followed by the pound key, the value of this parameter would be ww1234#. Remember to URL-encode this string, since the '#' character has special meaning in a URL. If both SendDigits and MachineDetection parameters are provided, then MachineDetection will be ignored.
The integer number of seconds that we should allow the phone to ring before assuming there is no answer. The default is 60 seconds and the maximum is 600 seconds. For some call flows, we will add a 5-second buffer to the timeout value you provide. For this reason, a timeout value of 10 seconds could result in an actual timeout closer to 15 seconds. You can set this to a short time, such as 15 seconds, to hang up before reaching an answering machine or voicemail.
Whether to record the call. Can be true to record the phone call, or false to not. The default is false. The recording_url is sent to the status_callback URL.
The number of channels in the final recording. Can be: mono or dual. The default is mono. mono records both legs of the call in a single channel of the recording file. dual records each leg to a separate channel of the recording file. The first channel of a dual-channel recording contains the parent call and the second channel contains the child call.
Whether to detect if a human, answering machine, or fax has picked up the call. Can be: Enable or DetectMessageEnd. Use Enable if you would like us to return AnsweredBy as soon as the called party is identified. Use DetectMessageEnd, if you would like to leave a message on an answering machine. If send_digits is provided, this parameter is ignored. For more information, see Answering Machine Detection.
The number of seconds that we should attempt to detect an answering machine before timing out and sending a voice request with AnsweredBy of unknown. The default timeout is 30 seconds.
The recording status events that will trigger calls to the URL specified in recording_status_callback. Can be: in-progress, completed and absent. Defaults to completed. Separate multiple values with a space.
The phone number, SIP address, or Client identifier that made this call. Phone numbers are in E.164 format (e.g., +16175551212). SIP addresses are formatted as name@company.com.
The number of milliseconds that is used as the measuring stick for the length of the speech activity, where durations lower than this value will be interpreted as a human and longer than this value as a machine. Possible Values: 1000-6000. Default: 2400.
The number of milliseconds of silence after speech activity at which point the speech activity is considered complete. Possible Values: 500-5000. Default: 1200.
Select whether to perform answering machine detection in the background. Default, blocks the execution of the call until Answering Machine Detection is completed. Can be: true or false.
The URL that we should call using the async_amd_status_callback_method to notify customer application whether the call was answered by human, machine or fax.
The SID of a BYOC (Bring Your Own Carrier) trunk to route this call with. Note that byoc is only meaningful when to is a phone number; it will otherwise be ignored. (Beta)
A token string needed to invoke a forwarded call. A call_token is generated when an incoming call is received on a Twilio number. Pass an incoming call's call_token value to a forwarded call via the call_token parameter when creating a new call. A forwarded call should bear the same CallerID of the original incoming call.
The audio track to record for the call. Can be: inbound, outbound or both. The default is both. inbound records the audio that is received by Twilio. outbound records the audio that is generated from Twilio. both records the audio that is received and generated by Twilio.
The absolute URL that returns the TwiML instructions for the call. We will call this URL using the method when the call connects. For more information, see the Url Parameter section in Making Calls.
Twimlstring<twiml>required if Url or ApplicationSid is not passed
TwiML instructions for the call Twilio will use without fetching Twiml from url parameter. If both twiml and url are provided then twiml parameter will be ignored. Max 4000 characters.
ApplicationSidSID<AP>required if Url or Twiml is not passed
{"ApplicationSid":"APaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa","FallbackMethod":"GET","FallbackUrl":"https://example.com","From":"+987654321","IfMachine":"if_machine","MachineDetection":"enable","MachineDetectionTimeout":15,"Method":"GET","Record":"true","RecordingTrack":"both","Trim":"do-not-trim","SendDigits":"send_digits","StatusCallback":"https://example.com","StatusCallbackMethod":"GET","Timeout":1,"To":"+123456789","Url":"https://example.com","CallerId":"Caller","MachineDetectionSpeechThreshold":3000,"MachineDetectionSpeechEndThreshold":3000,"MachineDetectionSilenceTimeout":3000,"AsyncAmd":"true","AsyncAmdStatusCallback":"http://statuscallback.com","AsyncAmdStatusCallbackMethod":"POST","MachineDetectionEngine":"Lumenvox","MachineDetectionMinWordLength":100,"MachineDetectionMaxWordLength":5000,"MachineDetectionWordsSilence":50,"MachineDetectionMaxNumOfWords":5,"MachineDetectionSilenceThreshold":256,"Byoc":"BYaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa","CallReason":"Reason for the call (Beta)","TimeLimit":3600,"CallToken":"call-token-string","Transcribe":"true","TranscriptionConfiguration":"JVaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa"}
Create a Call resource with TwiML
Provide TwiML instructions of what should happen when the call is connected.
Node.js
Python
C#
Java
Go
PHP
Ruby
twilio-cli
curl
_20
// Download the helper library from https://www.twilio.com/docs/node/install
_20
const twilio = require("twilio"); // Or, for ESM: import twilio from "twilio";
_20
_20
// Find your Account SID and Auth Token at twilio.com/console
_20
// and set the environment variables. See http://twil.io/secure
After completing an outbound call, Twilio will make an asynchronous HTTP request to the StatusCallback URL you specified in your request (if any).
Parameters sent to your StatusCallback URL
When Twilio sends its asynchronous request to your StatusCallback URL, it includes all of the following parameters:
Parameter
Description
CallSid
A unique identifier for this call, generated by Twilio.
AccountSid
Your Twilio account ID. It is 34 characters long, and always starts with the letters AC.
From
The phone number or client identifier of the party that initiated the call.
Phone numbers use E.164 formatting, meaning they start with a + and country code, e.g. +16175551212.
Client identifiers begin with the client: URI scheme; for example, on a call from a client named 'charlie' the From parameter will be client:charlie.
To
The phone number or client identifier of the called party.
Phone numbers use E.164 formatting, meaning they start with a + and country code, e.g. +16175551212.
Client identifiers begin with the client: URI scheme; for example, for a call to a client named 'joey', the To parameter will be client:joey.
CallStatus
A descriptive status for the call.
The value is one of the following: queued, initiated, ringing, in-progress, completed, busy, failed or no-answer.
ApiVersion
The version of the Twilio API used to handle this call.
For incoming calls, this is determined by the API version set on the dialed number.
For outgoing calls, this is the version used in the REST API request of the outgoing call.
Direction
A string describing the direction of the call:
inbound for inbound calls
outbound-api for calls initiated via the REST API
outbound-dial for calls initiated by a <Dial> verb.
ForwardedFrom
This parameter may be set when Twilio receives a forwarded call. The carrier who forwards the call determines the contents of the parameter.
Not all carriers support passing this information.
Some carriers provide this information when making a direct call to a Twilio number.
CallerName
This parameter is set when the IncomingPhoneNumber that received the call has set its VoiceCallerIdLookup value to true ($0.01 per lookup).
ParentCallSid
A unique identifier for the call that created this leg.
If this is the first leg of a call, this parameter is not included.
StatusCallbackEvent
If you specify any call progress events in the StatusCallbackEvent parameter, Twilio will make an asynchronous request to the StatusCallback URL you provided in your POST request.
The call progress events you can specify are:
Event
Description
initiated
Twilio removes your call from the queue and starts dialing.
ringing
The call starts ringing.
answered
The call is answered. If this event is specified, Twilio will send an in-progress status.
completed
The call is completed, regardless of the termination status (which can be busy, cancelled, completed, failed, or no-answer). If no StatusCallbackEvent is specified, completed is fired by default.
When these events occur, Twilio's StatusCallback request will also include these additional parameters:
Parameter
Description
CallStatus
A descriptive status for the call. The value is one of queued, initiated, ringing, in-progress, busy, failed, or no-answer. For more details, see the CallStatus values in our TwiML introduction.
Duration
The duration in minutes of the just-completed call; calls are billed by the minute. Only present in the completed event.
CallDuration
The duration in seconds of the just-completed call. Only present in the completed event.
SipResponseCode
The final SIP code for the call. For example, a number that was unreachable will return 404. If the Timeout value was reached before the call connected, this code will be 487.
RecordingUrl
The URL of the phone call's recorded audio. This parameter is included only if Record=true is set on the REST API request and does not include recordings initiated in other ways. RecordingUrl is only present in the completed event. The recording file may not yet be accessible when the Status Callback is sent.
Note:Use RecordingStatusCallback for reliable notification on when the recording is available for access.
RecordingSid
The unique ID of the Recording from this call. RecordingSid is only present with the completed event.
RecordingDuration
The duration of the recorded audio (in seconds). RecordingDuration is only present in the completed event. To get a final accurate recording duration after any trimming of silence, use RecordingStatusCallback.
Timestamp
The timestamp when the event fired, given as UTC in RFC 2822 format.
CallbackSource
A string that describes the source of the webhook. This is provided to help disambiguate why the webhook was made. On Status Callbacks, this value is always call-progress-events.
SequenceNumber
The order in which the events were fired, starting from 0. Although events are fired in order, they are made as separate HTTP requests, and there is no guarantee they will arrive in the same order.
(information)
Info
You can use the StatusCallback and StatusCallbackEvent features to track the call status of Programmable Voice calls only.
(information)
Info
To learn more about the StatusCallbackEvent parameter and what you can expect from Twilio during and after an outbound call, check out our overview page on making outbound calls.
RecordingStatusCallback
If you requested a recording of your outbound call and you specified a RecordingStatusCallback URL, Twilio will make a GET or POST request to that URL when the recording is available.
Parameters sent to your RecordingStatusCallback URL
Twilio will pass along the following parameters to your RecordingStatusCallback URL:
Parameter
Description
AccountSid
The unique identifier of the Account responsible for this recording.
CallSid
A unique identifier for the call associated with the recording. CallSid will always refer to the parent leg of a two-leg call.
RecordingSid
The unique identifier for the recording.
RecordingUrl
The URL of the recorded audio.
RecordingStatus
The status of the recording. Possible values are: in-progress, completed, absent.
RecordingDuration
The length of the recording, in seconds.
RecordingChannels
The number of channels in the final recording file as an integer. Possible values are 1, 2.
RecordingStartTime
The timestamp of when the recording started.
RecordingSource
The initiation method used to create this recording. For recordings initiated when Record=true is set on the REST API, OutboundAPI will be returned.
RecordingTrack
The audio track recorded. Possible values are inbound, outbound, or both.
RecordingStatusCallbackEvent
Just as you can specify call progress events with StatusCallbackEvent, you can also specify which recording status changes should trigger a callback to your application.
Available recording status values are:
Parameter
Description
in-progress
The recording has started.
completed
The recording is complete and available for access.
absent
The recording is absent and inaccessible.
This parameter defaults to completed. To specify multiple values, separate them with a space.
Only include calls that started on this date. Specify a date as YYYY-MM-DD in UTC, for example: 2009-07-06, to read only calls that started on this date. You can also specify an inequality, such as StartTime<=YYYY-MM-DD, to read calls that started on or before midnight of this date, and StartTime>=YYYY-MM-DD to read calls that started on or after midnight of this date.
Only include calls that started on this date. Specify a date as YYYY-MM-DD in UTC, for example: 2009-07-06, to read only calls that started on this date. You can also specify an inequality, such as StartTime<=YYYY-MM-DD, to read calls that started on or before midnight of this date, and StartTime>=YYYY-MM-DD to read calls that started on or after midnight of this date.
Only include calls that started on this date. Specify a date as YYYY-MM-DD in UTC, for example: 2009-07-06, to read only calls that started on this date. You can also specify an inequality, such as StartTime<=YYYY-MM-DD, to read calls that started on or before midnight of this date, and StartTime>=YYYY-MM-DD to read calls that started on or after midnight of this date.
Only include calls that ended on this date. Specify a date as YYYY-MM-DD in UTC, for example: 2009-07-06, to read only calls that ended on this date. You can also specify an inequality, such as EndTime<=YYYY-MM-DD, to read calls that ended on or before midnight of this date, and EndTime>=YYYY-MM-DD to read calls that ended on or after midnight of this date.
Only include calls that ended on this date. Specify a date as YYYY-MM-DD in UTC, for example: 2009-07-06, to read only calls that ended on this date. You can also specify an inequality, such as EndTime<=YYYY-MM-DD, to read calls that ended on or before midnight of this date, and EndTime>=YYYY-MM-DD to read calls that ended on or after midnight of this date.
Only include calls that ended on this date. Specify a date as YYYY-MM-DD in UTC, for example: 2009-07-06, to read only calls that ended on this date. You can also specify an inequality, such as EndTime<=YYYY-MM-DD, to read calls that ended on or before midnight of this date, and EndTime>=YYYY-MM-DD to read calls that ended on or after midnight of this date.
You can append a .csv extension to any resource URI to get CSV (Comma Separated Values) representation. Specifying CSV may be especially useful for call logs. Try this:
If you are using the Twilio REST API, the list returned to you includes paging information.
If you plan to request more records than will fit on a single page, you can use the provided nextpageuri rather than incrementing through pages by page number.
Using nextpageuri for paging ensures that your next request will pick up where you left off. This can help keep you from retrieving duplicate data if you are actively making or receiving calls.
(information)
Info
All of the Twilio Helper Libraries handle paging automatically. You do not need to explicitly request individual pages when using a Helper Library to fetch lists of resources.
Update a Call resource
POST https://api.twilio.com/2010-04-01/Accounts/{AccountSid}/Calls/{Sid}.json
Updating a Call resource allows you to modify an active call.
Real-time call modification allows you to interrupt an in-progress call and terminate it or have it begin processing TwiML from either a new URL or from the TwiML provided with modification. Call modification is useful for any application where you want to change the behavior of a running call asynchronously, e.g., hold music, call queues, transferring calls, or forcing a hangup.
By sending an HTTP POST request to a specific Call instance, you can redirect a call that is in progress or you can terminate a call.
(information)
Info
For step-by-step guidance on modifying in-progress calls, check out the tutorial Modify Calls in Progress in your web language of choice.
The absolute URL that returns the TwiML instructions for the call. We will call this URL using the method when the call connects. For more information, see the Url Parameter section in Making Calls.
The HTTP method we should use when calling the url. Can be: GET or POST and the default is POST. If an application_sid parameter is present, this parameter is ignored.
The new status of the resource. Can be: canceled or completed. Specifying canceled will attempt to hang up calls that are queued or ringing; however, it will not affect calls already in progress. Specifying completed will attempt to hang up a call even if it's already in progress.
The URL that we call using the fallback_method if an error occurs when requesting or executing the TwiML at url. If an application_sid parameter is present, this parameter is ignored.
The HTTP method that we should use to request the fallback_url. Can be: GET or POST and the default is POST. If an application_sid parameter is present, this parameter is ignored.
The URL we should call using the status_callback_method to send status information to your application. If no status_callback_event is specified, we will send the completed status. If an application_sid parameter is present, this parameter is ignored. URLs must contain a valid hostname (underscores are not permitted).
The HTTP method we should use when requesting the status_callback URL. Can be: GET or POST and the default is POST. If an application_sid parameter is present, this parameter is ignored.
When you redirect an active call to another phone number, Twilio creates an entirely new Call instance for that new phone number. The original call is the parent call, and any additional number dialed establishes a child call. Parent and child calls will have uniquely identifying Call SIDs.
Note that any parent call currently executing a <Dial> is considered in-progress by Twilio. Even if you've re-directed your initial call to a new number, the parent call is still active, and thus you must useStatus=completed to end it.
(warning)
Warning
If Enhanced SIP Features is not enabled on your account, unanswered child calls cannot be canceled via the REST API, but the parent call can be modified to point to new TwiML. This action will end the child call.
Update the StatusCallback of an active Call
Ensure that you also specify the URL when updating the StatusCallback
Node.js
Python
C#
Java
Go
PHP
Ruby
twilio-cli
curl
_19
// Download the helper library from https://www.twilio.com/docs/node/install
_19
const twilio = require("twilio"); // Or, for ESM: import twilio from "twilio";
_19
_19
// Find your Account SID and Auth Token at twilio.com/console
_19
// and set the environment variables. See http://twil.io/secure
Note: For calls less than 13 months old, resources deleted from this endpoint will also be deleted in Log Archives. Calls older than 13 months can only be deleted via the Bulk Export API.
Delete a Call resource
Node.js
Python
C#
Java
Go
PHP
Ruby
twilio-cli
curl
_14
// Download the helper library from https://www.twilio.com/docs/node/install
_14
const twilio = require("twilio"); // Or, for ESM: import twilio from "twilio";
_14
_14
// Find your Account SID and Auth Token at twilio.com/console
_14
// and set the environment variables. See http://twil.io/secure
You are able to retrieve resources via GET to the /Calls endpoint for 13 months after the resource is created. Records older than thirteen months can only be retrieved via Bulk Export.
We provide a Bulk Export utility in Console and via API. Bulk Export will generate S3 files containing one day of data per file and deliver the download link via webhook, email, or Console.