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Twilio Client SDK


The Twilio Client SDK lets you bring high-quality VoIP calling directly into your web and mobile applications. Use the Twilio Client SDKs to build click-to-call applications, soft phone services, contact center applications, and more.

Want to get started right away?

Jump right in with our Twilio Client Quickstart!

The twilio.js Library

Connect TwiML voice applications to the browser using the twilio.js Library.

Twilio Client iOS SDK

Add voice-over-IP to your iOS applications with the Twilio Client iOS SDK.

Twilio Client Android SDK

Add voice-over-IP to your Android applications with the Twilio Client Android SDK.

How It Works

You setup your device and establish a connection to Twilio. Audio from your device's microphone is sent to Twilio, and Twilio plays audio through your device's speakers, like on a normal phone call. But with Twilio Client, your device need not be a phone.

When you initiate a connection using Twilio Client, you're not connecting to another phone directly. Rather, you're connecting to Twilio and instructing Twilio to fetch TwiML from your server to handle the connection. This is analogous to the way Twilio handles incoming calls from a real phone. All the same TwiML verbs and nouns that are available for handling Twilio Voice calls are also available for handling Twilio Client connections. We've also added a new <Client> noun for dialing to a Client.

Twilio Applications

Because Twilio Client connections aren't made to a specific phone number, Twilio relies on a Twilio Application within your account to determine how to interact with your server. A Twilio Application is just a convenient way to store a set of URLs, like the VoiceUrl and SmsUrl on a phone number, but without locking them to a specific phone number. This makes Twilio Applications perfect for handling connections from Twilio Client (which is actually why we created them in the first place).

So when your device initiates a Twilio Client connection to Twilio, a request is made to the VoiceUrl property of an Application within your account. You specify the Application you're connecting to with a Capability Token. Twilio uses the TwiML response from its request to that Application's VoiceUrl to direct what happens with the Client connection.


Twilio Client SDK

Channel Type
Signaling WSS (TLS)

iOS & Android Voice SDK 3.0

Channel Type
Signaling TLSv1.2

iOS & Android Voice SDK 2.0

Channel Type
Signaling TLSv1.2
Media (SDES) SRTP (AES_CM_128/256_HMAC_SHA1_32/80)
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Need some help?

We all do sometimes; code is hard. Get help now from our support team, or lean on the wisdom of the crowd browsing the Twilio tag on Stack Overflow.


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