Hi there! I'm a senior iOS developer with over a decade of experience building mobile applications. I've been working with CallKit since its release and have helped numerous companies integrate it seamlessly into their apps.

Let's dive into what CallKit is all about.

What is CallKit?

CallKit, introduced by Apple in iOS 10, is a powerful framework that empowers VoIP (Voice over Internet Protocol) apps to enhance their system-level integration with iOS. Essentially, CallKit acts as a bridge between VoIP apps and the native phone app UI, providing a more seamless and intuitive calling experience for users.

Key Features and Benefits of CallKit:


1. Native Phone App Integration: CallKit's crown jewel is its ability to integrate VoIP calls directly into the native Phone app. This means:
- Incoming VoIP calls are displayed on the lock screen just like regular calls.
- Users can manage VoIP calls (answer, decline, mute, hold, etc.) using the familiar Phone app interface.
- VoIP calls are listed within the Phone app's Recents and Favorites, providing a unified call history.


2. Call Blocking and Identification: CallKit allows VoIP apps to leverage the system's call blocking and identification features.
- Users can block unwanted VoIP calls using the system's block list.
- VoIP apps can provide caller ID information, even for numbers not stored in the user's contacts.


3. Call Directory Extension: With CallKit, VoIP apps can provide a list of contacts that can be accessed directly from the native Phone app. This enhances user experience by allowing them to initiate VoIP calls without having to switch apps.


4. Improved Background Handling: CallKit optimizes background processing for VoIP apps, enabling them to receive calls more reliably even when not actively used.


5. Enhanced Audio Routing: CallKit provides access to advanced audio routing capabilities, ensuring high-quality audio during VoIP calls. Users can seamlessly switch between the device's speaker, Bluetooth headsets, and other audio output options.

How CallKit Works:

CallKit operates on the concept of "Call Directory Extensions" and "CXProvider" to manage call interactions.

- Call Directory Extension: This allows VoIP apps to register as a provider of contact information and handle call blocking.

- CXProvider: This protocol is the heart of CallKit integration, enabling VoIP apps to:
- Report incoming and outgoing calls to the system.
- Update call states (e.g., ringing, connected, on hold).
- Handle user actions like answering, declining, and ending calls.
- Start and end audio sessions.
- Manage call-related information, such as caller ID and call blocking.

Example Use Cases:

CallKit is incredibly versatile and can be leveraged by various apps:

- **VoIP Calling Apps (Skype, WhatsApp, Viber):** These apps heavily rely on CallKit for a native calling experience, seamless call management, and enhanced reliability.
- Call Blocking Apps: These apps use CallKit to integrate with the system's block list, allowing users to block unwanted calls from specific numbers.
- Business Phone Systems: Businesses can use CallKit to integrate their VoIP-based phone systems into employees' iPhones, providing a unified communication platform.

In a Nutshell:

CallKit is an indispensable framework for VoIP apps looking to deliver a seamless, native-like calling experience on iOS. By bridging the gap between VoIP functionality and the native Phone app, CallKit empowers developers to create feature-rich and user-friendly communication solutions.

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CallKit is a new framework that lets your VoIP app integrate tightly with the native Phone UI. Learn how you can have your incoming calls displayed fully on the lock screen. Get details on how people can choose to use your app when making calls from the native Phone app's contacts, favorites, and recents.read more >>