TwiML™ Voice: <Conference>
<Conference> noun allows you to connect to a conference
room. Much like how the
<Number> noun allows you to connect to another phone
<Conference> noun allows you to connect to a named conference
room and talk with the other callers who have also connected to that room. Conference is commonly used as a container for calls when implementing hold, transfer, and barge.
Twilio offers a globally distributed, low latency conference system that hosts your conferences in the region closest to the majority of your participants and has a maximum participant capacity of 250. It has a per-participant-per-minute price in addition to standard voice minute pricing. Learn more about Conference pricing.
The name of the room is up to you and is namespaced to your account. This
means that any caller who joins
room1234 via your account will end up in
the same conference room, but callers connecting through different accounts would not.
For compliance reasons, do not use personal data (also known as personally identifiable information), such as phone numbers, email addresses, or a person’s name, or any other sensitive information when naming the conferences
By default, Twilio conference rooms enable a number of useful features that can be enabled or disabled based on your particular needs:
- Conferences will not start until at least two participants join.
- While waiting, customizable background music is played.
- When participants join and leave, notification sounds are played to inform the other participants.
- Events can be configured to alert your application to state changes in a conference
- Receive a webhook when a participant speaks or stops speaking
You can configure or disable each of these features based on your particular needs.
<Conference> noun supports the following attributes that modify its behavior:
|Attribute Name||Allowed Values||Default Value|
|beep||true, false, onEnter, onExit||true|
|participantLabel||a label for the conference participant||None|
|jitterBufferSize||small, medium, large, off||large|
|waitUrl||TwiML URL, empty string||default Twilio hold music|
|waitMethod||GET or POST||POST|
|maxParticipants||positive integer <= 250||250|
|record||do-not-record or record-from-start||do-not-record|
|region||us1, ie1, de1, sg1, br1, au1, jp1||None|
|trim||trim-silence or do-not-trim||trim-silence|
|coach||A Call SID||none|
|statusCallbackEvent||start end join leave mute hold modify speaker announcement||None|
|statusCallback||relative or absolute URL||None|
|recordingStatusCallback||relative or absolute URL||None|
|recordingStatusCallbackEvent||in-progress, completed, absent||completed|
|eventCallbackUrl||relative or absolute URL||None|
muted attribute lets you specify whether a participant can speak on the
conference. If this attribute is set to
true, the participant will only be
able to listen to people on the conference. This attribute defaults to
To change a conference participant's muted attribute during a call use to the Conference Participant API.
beep attribute lets you specify whether a notification beep is played to
the conference when a participant joins or leaves the conference. Defaults to
|true||Default. Plays a beep both when a participant joins and when a participant leaves.|
|false||Disables beeps for when participants both join and exit.|
|onEnter||Only plays a beep when a participant joins. The beep will not be played when the participant exits.|
|onExit||Will not play a beep when a participant joins; only plays a beep when the participant exits.|
This attribute tells a conference to start when this participant joins the
conference, if it is not already started. This is
true by default. If this is
false and the participant joins a conference that has not started, they are
muted and hear background music until a participant joins where
true. This is useful for implementing moderated
If a participant has this attribute set to
true, then when that participant
leaves, the conference ends and all other participants drop out. This
false. This is useful for implementing moderated conferences that
bridge two calls and allow either call leg to continue executing TwiML if the
other hangs up.
A unique label for the participant which will be added into the conference as a result of executing the TwiML. The label provided here can be used subsequently to read or update participant attributes using the Twilio REST API. The participantLabel must be unique across all participants in the conference, and there is a max limit of 128 characters.
If a participant with the same label already exists in the conference, 16025 error notification will be reported, and visible on Twilio Console. The call will not be added into the conference and instead continue to the next TwiML verb.
jitterBufferSize attribute lets you set the jitter buffer behavior for a conference participant. Twilio Conference uses a jitter buffer to smooth out irregularity in media packet arrival times when mixing audio for conference participants. This buffer results in fewer audio artifacts, but introduces a fixed delay for the audio of each participant.
jitterBufferSize value to
small will create a 20ms buffer that results in average latency of ~150ms - ~200ms on a stream with max jitter of ~20ms.
Setting the value to
medium will create a 40ms buffer that results in average latency of ~200ms - ~360ms on a stream with max jitter of ~20ms.
large setting, which is the default jitter buffer behavior, will create a 60ms buffer that results in average latency between ~300ms - ~1000ms on a stream with max jitter of ~20ms.
Spikes of extremely high jitter can result in the maximum latency exceeding the average latency by as much as 50%.
off setting completely disables the buffer and packets with relatively low jitter ( <=20ms) will be completely dropped, but Twilio will add no extra latency when mixing.
The buffer value is a particpant-level setting, the value for participant A does not apply to participant B.
waitUrl attribute lets you specify a URL for music that plays before the
conference has started. The URL may return an MP3 file, a WAV file, or a TwiML document that contains
<Redirect> verbs. If the
waitUrl responds with TwiML,
<Gather> verbs are not allowed. This defaults to a selection of Creative Commons licensed background music, but you can replace it with your own music and messages. If you do not wish anything to play while waiting for the conference to start, specify the empty string (set
waitUrl is specified, Twilio will use its own HoldMusic Twimlet that reads a public AWS S3 Bucket for audio files. The default
waitUrl is: http://twimlets.com/holdmusic?Bucket=com.twilio.music.classical
Please note, if the request to your waitUrl fails, the Conference will not be fully established. To avoid the call being disconnected, you can either add additional TwiML after the initial
<Conference>, or programmatically provide fallback behavior via the action callback.
This URL points at S3 bucket com.twilio.music.classical, containing a selection of nice Creative Commons classical music. Here's a list of S3 buckets we've assembled with other genres of music for you to choose from:
This attribute indicates which HTTP method to use when requesting
defaults to 'POST'. Be sure to use 'GET' if you are directly requesting static
audio files such as WAV or MP3 files so that Twilio properly caches the files.
This attribute indicates the maximum number of participants you want to allow within a named conference room. The maximum number of participants is 250.
record attribute lets you record an entire
<Conference>. When set to
record-from-start, the recording begins when the first two participants are
bridged. The hold music is never recorded. If a
recordingStatusCallback URL is given,
Twilio will make a request to the specified URL with recording details when the recording is available to access.
region attribute specifies the region where Twilio should mix the conference. Specifying a value for region overrides Twilio's automatic region selection logic and should only be used if you are confident you understand where your conferences should be mixed. Twilio sets the region parameter from the first participant that specifies the parameter and will ignore the parameter from subsequent participants.
trim attribute lets you specify whether to trim leading and trailing
silence from your audio files.
trim defaults to
trim-silence, which removes
any silence at the beginning or end of your recording. This may cause the
duration of the recording to be slightly less than the duration of the call.
Coach accepts a call SID of a call that is currently connected to an in-progress conference. Specifying a call SID that does not exist or is no longer connected to the conference will result in the call failing to the action URL and throwing a 13240 error.
statusCallbackEvent attribute allows you to specify which conference state changes should generate a Webhook to the URL specified in the
statusCallback attribute. The available values are
announcement. To specify multiple values separate them with a space. Events are set by the first Participant to join the conference, subsequent statusCallbackEvents will be ignored. If you specify conference events you can see a log of the events fired for a given conference in the conference logs in the console.
|start||The conference has begun and audio is being mixed between all participants. This occurs when there are at least two participants in the conference, and at least one of the participants has
|end||The last participant has left the conference or a participant with
|join||A participant has joined the conference.|
|leave||A participant has left the conference.|
|mute||A participant has been muted or unmuted.|
|hold||A participant has been held or unheld.|
|modify||At least one of a participant's attributes has been modified:
|speaker||A participant has started or stopped speaking.|
|announcement||A participant or conference announcement has ended or failed. Currently, the
statusCallback attribute takes a URL as an argument. Conference events specified in the
statusCallbackEvent parameter will be sent to this URL.
statusCallback URL is set by the first Participant to join the conference, subsequent setting of the
statusCallback will be ignored.
The parameters contained in the events requests are detailed below.
The HTTP method Twilio should use when requesting the above URL. Defaults to POST
Twilio will pass the following parameters with its request to the
statusCallback URL. For participant announcement events, Twilio will pass additional participant-related request parameters if the participant being announced to is still present in the conference.
|ConferenceSid||CFe08c870b500f6e44a9ad184defd1f391||Sent on: All|
|FriendlyName||MyConf||Sent on: All|
|AccountSid||AC25e16e9a716a4a8617a7c83f58e30482||Sent on: All|
|SequenceNumber||1||Sent on: All|
|Timestamp||Thu, 1 Jun 2017 20:48:32 +0000||Sent on: All|
|Sent on: join leave start end mute hold modify speaker announcement|
|CallSid||CA25e16e9a716a4a1786a7c83f58e30482||Sent on: join leave mute hold modify speaker announcement (for participant announcements)|
|Muted||true, false||Sent on: join leave mute hold modify speaker announcement (for participant announcements)|
|Hold||true, false||Sent on: join leave mute hold modify speaker announcement (for participant announcements)|
|Coaching||true, false||Sent on: join leave mute hold modify speaker announcement (for participant announcements)|
|EndConferenceOnExit||true, false||Sent on: join leave mute hold modify speaker announcement (for participant announcements)|
|StartConferenceOnEnter||true, false||Sent on: join leave mute hold modify speaker announcement (for participant announcements)|
|CallSidEndingConference||Call SID of the participant who ended the conference (if applicable)||Sent on: end|
|ParticipantLabelEndingConference||Label of the participant who ended the conference (if applicable)||Sent on: end|
|Sent on: end|
|Reason||A message indicating why the conference ended||Sent on: end|
|ReasonAnnouncementFailed||A message indicating why the announcement failed||Sent on: announcement|
|AnnounceUrl||The URL used for the announcement||Sent on: announcement|
|EventName*||conference-record-end||Sent on: conference-record-end|
|RecordingUrl*||https://api.twilio.com/2010-04-01/Accounts/AC123/Recordings/RE234||Sent on: conference-record-end|
|Duration*||6||Sent on: conference-record-end|
|RecordingFileSize*||90786||Sent on: conference-record-end|
conference-record-end parameters above have been deprecated in favor of
recordingStatusCallback, which is the preferred approach to receive recording related information. Providing a
recordingStatusCallback will result in no
recordingStatusCallback attribute takes a relative or absolute URL as an argument.
If a conference recording was requested via the record attribute and a
recordingStatusCallback URL is given, Twilio will make a GET or POST request to the specified URL when the recording is available to access.
Twilio will pass the following parameters with its request to the
|AccountSid||The unique identifier of the Account responsible for this recording.|
|ConferenceSid||A unique identifier for the conference associated with the recording.|
|RecordingSid||The unique identifier for the recording.|
|RecordingUrl||The URL of the recorded audio.|
|RecordingStatus||The status of the recording. Possible values are:
|RecordingDuration||The length of the recording, in seconds|
|RecordingChannels||The number of channels in the final recording file as an integer. Only
|RecordingStartTime||The timestamp of when the recording started.|
|RecordingSource||The initiation method used to create this recording.
This attribute indicates which HTTP method to use when requesting
recordingStatusCallback. It defaults to 'POST'.
This attribute allows you to specify which recording status changes should generate a webhook to the URL specified in the
recordingStatusCallback attribute. The available values are
absent. To specify multiple values separate them with a space. Default is
Details on the status change events below:
|in-progress||The recording has started|
|completed||The recording is complete and available for access|
|absent||The recording is absent and not accessible|
To pause or resume conference recordings, see the Recording API Docs.
This parameter has been deprecated in favor of recordingStatusCallback. Providing a recordingStatusCallback will result in no eventCallback.
The 'eventCallbackUrl' attribute takes a URL as an argument. When the conference ends, Twilio will make a POST request to this URL with the
conference-record-end event parameters of statusCallback.
Example 1: A Simple Conference
By default, the first caller to execute this TwiML would join the conference room named Room 1234 and listen to the default waiting music. When the next caller executed this TwiML, they would join the same conference room and the conference would start. The default background music ends, the notification beep is played and all parties can communicate.
Example 2: A Moderated Conference
First, you can drop a number of people into the conference, specifying that the conference shouldn't yet start:
Each person will hear hold music while they wait. When the "moderator" or conference organizer calls in, you can specify that the conference should begin:
Also note that since the moderator has "endConferenceOnExit='true'" set, then when the moderator hangs up,
the conference will end and each participant's
<Dial> will complete.
Example 3: Join an Evented Conference
This code will put you into a conference where events will be fired on the start, end, join, leave, mute, and hold state changes of the participant and conference.
Example 4: Join a Conference Muted
This code allows participants to join the conference room muted. They can hear what unmuted participants are saying but no one can hear them. The muted attribute can be enabled or disabled in realtime via the REST API.
Example 5: Bridging Calls
Sometimes you just want to bridge two calls together without any of the bells and whistles. With this minimal conferencing attribute setup, no background music or beeps are played, participants can speak right away as they join, and the conference ends right away if either participant hangs up. This is useful for cases like bridging two existing calls, much like you would with a Dial.
This code puts the first caller into a waiting room, where they'll hear music. It's as if they're on hold, waiting for an agent or operator to help them.
Then, when the operator or agent is ready to talk to them... their call would execute:
This code would join the operator with the person who was holding. Because the conference starts when they enter, the wonderful hold music the first person was hearing will stop, and the two people will begin talking. Because "beep='false'", the caller won't hear a ding when the agent answers, which is probably appropriate for this use case. When the operator hangs up, then 'endConferenceOnExit' will cause the conference to end.
Example 7: Combining with Dial attributes
Because Conference is an element of Dial, you can still use all the Dial attributes in combination with Conference (with the exception of callerId and timeout, which have no effect). You can set a timeLimit, after which you'll be removed from the conference. You can turn on hangupOnStar, which lets you leave a conference by pressing the * key. You can specify an action, so that after you leave the conference room Twilio will submit to the action and your web server can respond with new TwiML and continue your call.
Example 8: Recording a Conference
This code allows you to record an entire conference starting when the first two participants are bridged and will send a recordingStatusCallback when the conference recording is available for access.
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