If you've ever built a VoIP (Voiceover Internet Protocol) app for iOS, you know the struggle. Users expect VoIP calls to behave just like regular phone calls – ringing even when the app is closed, showing up in the call history, and allowing them to answer from the lock screen. But without the right integration, VoIP calls on an iPhone can feel clunky and frustrating to use.
This is where CallKit iOS comes in. Apple CallKit enables developers to integrate calls with the phone app, making VoIP calls feel native. But while CallKit API solves many VoIP challenges, it also comes with limitations – strict user consent requirements, privacy restrictions, and limited UI customization. For some apps, these restrictions make a custom VoIP client for iOS a better alternative.
In this article, we’ll cover what CallKit is, how it enhances VoIP calls on iPhone, its advantages and drawbacks, and when a custom VoIP solution might be the better choice. If you're looking to integrate CallKit into your app – or build a more advanced VoIP system – you’ll find everything you need to know right here.
You can get in touch with us anytime with any questions related to chat apps and messaging systems.
Understanding the CallKit API
If you're wondering, “What is CallKit?”, it’s Apple’s framework for enabling VoIP calls to integrate seamlessly with the iPhone’s native phone app. CallKit iOS allows VoIP apps to present calls just like standard cellular calls, making it easier for users to manage VoIP calls without opening a separate app.
Before Apple CallKit, VoIP apps had to create their own custom interfaces for answering and managing calls. This often resulted in a fragmented experience where incoming VoIP calls would be easy to miss, especially if the app wasn’t running in the foreground. CallKit API solves this problem by letting VoIP apps integrate directly with iOS’s built-in call system, ensuring VoIP calls appear on the lock screen, in the call history, and even work with Bluetooth headsets and CarPlay. It bridges the gap between VoIP and the iPhone’s built-in phone features.
How CallKit API works
CallKit API is not a VoIP service itself – it doesn’t handle call transmission. Instead, it acts as a bridge between a VoIP client on iOS (using WebRTC or another backend – we wrote a full article dedicated to chat app architecture if you’d like to explore this topic further) and the iOS system UI. It provides:
- System-level call UI – incoming and outgoing VoIP calls look and behave like regular phone calls.
- Call history integration – VoIP calls appear in the iPhone’s call log alongside standard calls.
- Call controls – users can mute, hold, and merge VoIP calls just like cellular calls.
- PushKit support – incoming VoIP calls can wake up the app efficiently without excessive background processing.
- Call blocking and identification – apps can filter unwanted calls or provide caller identification services.
For businesses building a VoIP client on iOS, CallKit API is a game-changer. It eliminates the need for custom call UI development, enhances user experience, and ensures VoIP calls on iPhone function as seamlessly as possible. However, like most technologies, CallKit iOS has significant advantages as well as strict requirements and limitations. Let’s look at its pros first.
How CallKit enhances VoIP calls on iPhone
Integrating CallKit into a VoIP app transforms the user experience by making VoIP calls on iPhone feel like native phone calls. Instead of requiring users to unlock their device, open an app, and manually accept a call, CallKit enables incoming VoIP calls to appear on the lock screen and behave just like regular cellular calls.
Key Features of CallKit API
Native call UI and seamless call handling
Without CallKit, VoIP apps must build their own call interfaces, which can be inconsistent and confusing for users. CallKit API eliminates this issue by providing a familiar, system-wide call interface. Users can answer calls directly from the lock screen, switch between VoIP and cellular calls, and even merge calls for conferencing – without needing to open the app.
Call history and phone app integration
VoIP calls on iPhone are no longer isolated to the app that placed them. With CallKit, all VoIP calls are logged in the native call history, making it easy for users to see their call records, redial numbers, and manage contacts. This integration ensures that VoIP calls are treated just like regular phone calls.
Improved battery efficiency with PushKit
Running a VoIP app in the background drains battery life, but CallKit works with PushKit to minimize power consumption. Instead of keeping an app running constantly, PushKit allows VoIP apps to receive a notification when an incoming call arrives, waking up the app only when needed. This method reduces unnecessary background activity while ensuring reliable call delivery.
Apple ecosystem compatibility
CallKit enables VoIP calls to work seamlessly across Apple’s ecosystem, including:
- Siri integration, allowing users to place VoIP calls via voice commands.
- CarPlay and Apple Watch compatibility, enabling hands-free call management.
- Bluetooth support, so users can answer VoIP calls using wireless headsets.
Leveraging these features of CallKit makes it possible for a VoIP client on iOS to deliver a polished, professional, and fully integrated calling experience. However, while CallKit offers significant advantages, it also comes with limitations that developers must navigate. In the next section, we’ll explore these constraints and when a custom VoIP solution might be the better option.
Benefits of using Apple CallKit for VoIP iOS apps
For any developer building a VoIP client on iOS, integrating CallKit is one of the most effective ways to enhance the user experience and streamline call management. By allowing VoIP calls on iPhone to behave like standard cellular calls, CallKit significantly improves usability, engagement, and reliability.
A seamless, native UX
Users expect phone calls to work in a certain way. Without CallKit, VoIP calls require opening a separate app to answer or make a call, which can feel unnatural and inconvenient. With CallKit, incoming VoIP calls appear on the lock screen, outgoing calls are dialed through the native interface, and users can handle VoIP calls just like any other call.
Unified call history and contact integration
One of the biggest advantages of CallKit is that it integrates VoIP calls into the iPhone’s call log. This means VoIP calls are visible in the same history as cellular calls, making it easier for users to track their conversations, return calls, and manage contacts.
Better battery efficiency with PushKit
Running a VoIP app in the background to listen for incoming calls drains battery life. CallKit solves this issue by working with PushKit, which allows the app to remain inactive until a VoIP call is received. This ensures efficient power usage while maintaining reliable call functionality.
Apple ecosystem compatibility
CallKit enhances VoIP apps by making them compatible with Apple’s broader ecosystem:
- Works with Siri, enabling hands-free calling through voice commands.
- Supports CarPlay, so users can manage VoIP calls while driving.
- Integrates with Apple Watch, allowing calls to be handled from the wrist.
- Enables Bluetooth headset support, making VoIP calls feel just like standard phone calls.
Improved call management features
CallKit allows VoIP calls to support:
- Call merging and conference calls.
- Call waiting and switching between VoIP and cellular calls.
- Holding and muting calls directly through the system dialer.
Increased adoption and trust
Users are more likely to trust and use a VoIP app when it behaves like the built-in phone app. CallKit removes friction, making VoIP adoption easier for users who might otherwise find a separate VoIP client confusing or inconvenient.
While CallKit provides many advantages, it is not without its limitations. In the next section, we will examine the restrictions developers face when using CallKit and when a custom VoIP solution might be necessary.
Limitations of CallKit iOS: what you need to know
While CallKit significantly enhances the user experience for VoIP calls on iPhone, it also introduces certain restrictions that developers must consider. Apple enforces strict guidelines on how CallKit can be used, and in some cases, these limitations may require a more customized VoIP solution.
User consent is required
Unlike traditional cellular calls, CallKit requires explicit user permission to handle VoIP calls. When an app first requests CallKit access, users must approve it in their settings. If a user denies this permission, VoIP calls will not appear in the native phone interface, limiting the app’s functionality.
No access to call logs or call audio
For privacy reasons, CallKit does not provide access to call logs or call recordings. While CallKit allows a VoIP call to be displayed in the iPhone’s call history, the app itself cannot retrieve or analyze this data. Additionally, CallKit does not process call audio, meaning developers must rely on external VoIP protocols such as WebRTC or SIP to handle the actual call transmission.
Limited UI customization
CallKit enforces the use of Apple’s native phone UI for incoming and outgoing calls. This means VoIP apps cannot customize the look and feel of the call screen beyond basic branding elements like the app name and icon. For companies that require a unique user interface or custom call-handling features, this can be a major constraint.
Compliance with App Store policies
Apple has strict policies regarding VoIP services, particularly regarding call handling and background activity.
- PushKit requirement: all incoming VoIP calls must be handled through Apple’s PushKit framework. Using alternative background processes to maintain call connections can result in an app being rejected from the App Store.
- Privacy and data restrictions: apps must comply with Apple’s privacy guidelines, which limit how call data can be used or shared.
Regional restrictions on CallKit usage
In some countries, CallKit functionality is restricted or outright banned due to government regulations. For example, China does not allow CallKit integration, meaning VoIP apps targeting that market must use alternative call-handling methods. This can be a challenge for global VoIP services that need a consistent experience across different regions.
Not a full VoIP solution
While CallKit improves VoIP call handling, it does not provide the actual VoIP infrastructure. Developers must still implement a separate VoIP engine – such as WebRTC, SIP, or a cloud-based telephony service – to manage call transmission, audio processing, and connectivity. CallKit simply enables the iPhone’s native interface to interact with these systems.
For many apps, these limitations may not be an issue. However, businesses that require enhanced security, deeper call analytics, or a custom user experience may need to consider a custom VoIP client for iOS. In the next section, we will explore when a fully customized VoIP solution might be the better choice.
How to enable VoIP calls with CallKit in a native iOS app
Integrating CallKit iOS into a VoIP app involves setting up the CallKit API, handling incoming and outgoing calls, and ensuring proper interaction with the native phone app. Below is a step-by-step guide.
- Import the necessary frameworks
To start using CallKit, import the required frameworks in your project:
- Set up CXProvider to handle calls
The CXProvider class is responsible for managing call events. You need to configure it and define a delegate to handle call actions.
- Use CXCallController to manage calls
To initiate calls from your app, use CXCallController to request actions like starting or ending a call.
- Handle incoming VoIP calls with PushKit
Since CallKit requires VoIP apps to use PushKit for incoming call notifications, register for PushKit notifications to wake up the app when an incoming call arrives.
- Configure background modes for VoIP
In your app’s Info.plist, enable the following background modes:
- Audio, AirPlay, and Picture in Picture
- Voice over IP (VoIP)
This ensures that the app can handle incoming calls even when it’s not actively running.
- Request user permissions for CallKit
When the app first launches, ensure that CallKit has permission to manage VoIP calls:
If users deny permissions, they must manually enable CallKit access in their iPhone settings.
- Test the CallKit integration
To verify that your integration is working correctly:
- Ensure PushKit is correctly receiving VoIP push notifications.
- Place outgoing calls using CXCallController and confirm they appear in the native call UI.
- Simulate incoming calls using CXProvider and confirm they appear on the lock screen.
When a custom VoIP solution might be better
While CallKit iOS offers a seamless way to integrate VoIP calls on iPhone with the native phone app, it is not always the best solution for every use case. Some applications require additional security, customization, or functionality that CallKit alone cannot provide. In these cases, a custom VoIP client for iOS may be the better option. What are the advantages of a custom solution?
Enhanced security and privacy
CallKit does not provide built-in encryption or advanced security features for VoIP calls. If your app requires end-to-end encryption, custom call authentication, or compliance with industry regulations such as HIPAA or GDPR, a custom VoIP solution with a secure backend is essential.
Custom call UI and UX
Apple CallKit enforces the use of the default iOS call interface, limiting branding and customization options. For companies that want to provide a unique call experience – such as business applications with integrated CRM features, specialized workflows, or unique in-call controls – a fully custom VoIP interface is necessary.
Advanced call routing and call management
CallKit supports basic call controls, but it lacks features such as intelligent call routing, IVR systems, or advanced call analytics. Businesses that require custom call handling, such as automated call distribution, call recording, or integration with third-party software like helpdesk or customer support systems, may need a more tailored solution.
No regional restrictions
Since CallKit API is restricted in some regions, such as China, businesses operating in these markets may need an alternative approach to ensure reliable VoIP services. A custom solution can bypass CallKit’s limitations while still providing a high-quality VoIP experience.
Greater control over call data and analytics
CallKit does not allow apps to access call logs or call metadata. If a business needs detailed call tracking, analytics, or reporting, a custom VoIP system that logs and processes call data independently of Apple’s restrictions is the only way to achieve this.
Enterprise and business communication needs
Many enterprise-level applications require deep integration with internal communication tools, team collaboration features, and secure conferencing options. A custom VoIP system can provide:
- Private company-wide VoIP networks.
- Secure internal communication without reliance on third-party services.
- Custom-built call encryption and authentication.
Making the right choice
If your goal is to provide a simple, native-like experience for standard VoIP calls, CallKit iOS is an excellent choice. However, if you need more control over security, customization, and functionality, a fully custom VoIP solution may be the only way to meet your business requirements.
How we can help with CallKit API & VoIP iOS development
Integrating CallKit iOS into a VoIP app requires a deep understanding of Apple's frameworks, VoIP protocols, and backend infrastructure. A poorly implemented CallKit API integration can lead to missed calls, unreliable call handling, or even App Store rejections. That’s why working with experts who specialize in VoIP calls on iPhone and custom VoIP client development for iOS is essential.
Our expertise in CallKit and VoIP iOS development
We have extensive experience in chat application development, including building VoIP clients for iOS that leverage CallKit API for seamless integration with the native phone app. Whether you need a simple CallKit video call implementation or a full-scale custom VoIP system, we provide:
- CallKit API integration to make VoIP calls feel native.
- Custom VoIP solutions for businesses needing enhanced security, call management, or custom interfaces.
- PushKit optimization to ensure battery-efficient call handling.
- End-to-end VoIP development using WebRTC, SIP, and cloud-based telephony services.
- Enterprise VoIP solutions with advanced call routing, analytics, and encryption.
Your VoIP app, built the right way
Building a VoIP client for iOS that works seamlessly with CallKit API requires more than just basic app development. It takes expertise in VoIP protocols, Apple’s strict guidelines, and real-world performance optimization. Whether you’re looking to integrate CallKit into your existing VoIP app or develop a custom VoIP solution from the ground up, we can help.
Get in touch today through this contact form to discuss your project and find the best solution for your VoIP app. Let’s build a system that meets your needs – without the technical headaches.
