WhatsApp is one of the most popular messaging apps in the world, with over 2 billion users globally. Originally launched in 2009, WhatsApp has grown exponentially while retaining its focus on secure messaging and voice/video calling. But what programming languages and frameworks were used to build WhatsApp and power its global infrastructure? Let’s take a closer look.
Overview of WhatsApp
WhatsApp is a cross-platform centralized instant messaging and voice over IP service owned by Meta Platforms. It allows users to send text messages, voice messages, make voice and video calls, and share images, documents, user locations and other content with individuals or groups. WhatsApp runs on a variety of platforms including Android, iOS, Web, KaiOS, and multi-platform desktop applications. Some key features and capabilities of WhatsApp include:
- End-to-end encryption for messages and calls
- Group chats with up to 256 participants
- Multimedia sharing (photos, videos, documents, etc.)
- Voice and video calls
- Push notifications to alert users of new messages and calls
- Status updates similar to stories on other platforms
- Cross-platform functionality across mobile and desktop
As of 2022, WhatsApp handles over 100 billion messages per day totaling over 63 million minutes of voice and video calls made daily. This massive scale and usage requires efficient and robust backend infrastructure and programming languages.
Programming Languages Behind WhatsApp
So what programming languages and frameworks are used to build WhatsApp clients and scale its backend infrastructure? The core WhatsApp clients (mobile apps and Web client) are built using these primary programming languages and frameworks:
- Erlang – For the backend server and infrastructure
- Objective-C – For iOS app development
- Java – For Android app development
- JavaScript – For Web client development
Erlang
The WhatsApp backend infrastructure largely runs on Erlang VM (BEAM) with servers written in Erlang. Erlang is a general-purpose, concurrent, functional programming language known for achieving high availability, distribution, fault tolerance and scalability. Key properties that make Erlang suitable for WhatsApp backend include:
- Built-in support for concurrency, distribution and fault tolerance
- Fast parallelization with lightweight processes
- Real-time messaging and clustering abilities
- Hot code loading for rapid development and deployment
- Scalability for distributed systems
WhatsApp leverages the fast real-time messaging capacities of Erlang to handle its enormous volumes of chat messaging, multimedia sharing, group chats, and voice/video calls across its global user base. The lightweight processes facilitate massive concurrency for handling these real-time messaging workloads. Erlang’s strength with distributed systems allows WhatsApp to scale massively across its server infrastructure.
Objective-C
Objective-C is the core language behind WhatsApp for iOS on Apple platforms like iPhone. It is the main programming language used for building apps on Apple’s Cocoa and Cocoa Touch frameworks. As WhatsApp was originally built for iPhone before expanding to other platforms, Objective-C enabled fast development leveraging Apple’s robust frameworks. Key advantages of Objective-C for iOS development include:
- Seamless integration with Cocoa/Cocoa Touch frameworks
- Strict superset of C allowing mix of OOP and procedural code
- Dynamic runtime enabling rapid prototyping
- Reference counting memory management
- Fast execution speed comparable to C
By leveraging Apple’s native frameworks with Objective-C, WhatsApp can deliver a highly optimized messaging experience on iOS. The mix of OOP and procedural programming facilitates flexibility in the codebase. The reference counting memory management also enables smooth performance in resource-constrained mobile devices.
Java
For WhatsApp on Android, the client is built natively using Java as the primary language. Java is the officially supported language for developing Android apps. As most of WhatsApp’s initial user growth was on Android in emerging markets, Java enabled fast development of an optimized Android app. Key advantages of Java for Android include:
- Official language for Android with rich SDK
- Object-oriented code that is familiar to many developers
- Strong community support and abundant libraries
- Memory management without risk of leaks or crashes
- Fast performance with JIT compilation
- Easy porting to other JVM platforms like Web servers
Java allowed WhatsApp to leverage Google’s rich Android frameworks to build a messaging app native to the platform. The OOP approach and garbage collected memory management enabled fast development. And Java skills are widely available, making it easier to build an Android team.
JavaScript
For the WhatsApp Web client that runs in browsers, it is built primarily using JavaScript. JavaScript allowed WhatsApp to make their service available through a Web client that requires no download. Key benefits of using JavaScript for the WhatsApp Web client include:
- Runs natively in all major browsers with no plugins
- Very fast execution time as a scripting language
- Asynchronous programming style
- Easy to connect to Web services and APIs
- Can dynamically update web page content
By leveraging JavaScript for Web development, WhatsApp was able to make their messaging available through a simple website. The asynchronous programming style of JavaScript is well-suited for messaging applications. And JavaScript allowed easy integration with the WhatsApp Web APIs to send and receive messages through the browser.
Other Languages and Frameworks
In addition to the core programming languages outlined above, WhatsApp development involves several other languages and frameworks:
- C/C++ – For performance-critical components
- Python – For prototype development and tools
- FreeBSD – To host custom versions of OpenBSD tools
- PHP – To develop the WhatsApp Web client and API
- Go – For newer server components at WhatsApp
- React Native – For cross-platform mobile app development
- MySQL – For data storage and queries
- Hadoop – For large scale data processing
- Tornado – As the messaging server
- Redis – For in-memory data structure store
C, C++, Python and Go allow WhatsApp developers to optimize performance for computationally intensive tasks. Tools like React Native facilitate building mobile apps across iOS and Android. MySQL, Hadoop, Redis and Tornado enable managing messaging data across large scale databases and servers.
Key Considerations
When evaluating programming languages and frameworks for an app like WhatsApp, some key considerations include:
- Scale – Ability to support large user base and message volumes
- Speed – Fast execution for responsive apps
- Concurrency – Facilitate many parallel real-time messaging conversations
- Distribution – Deploy across many servers and data centers
- Optimization – For mobile devices with limited resources
- Code reuse – Where possible across platforms like iOS, Android and Web
- Developer skills – Languages developers know to facilitate hiring
WhatsApp chose Erlang, Objective-C, Java and JavaScript as its primary languages because they best fit the criteria above. The combination enabled scale, speed, distribution, optimization and code reuse across its web, mobile and backend infrastructure.
Conclusion
WhatsApp leverages Erlang for its reliable real-time messaging backend, Objective-C and Java for native iOS and Android clients, and JavaScript for its Web client. These programming language choices allowed WhatsApp to scale its product across platforms to over 2 billion users while optimizing performance, concurrency, distribution and development velocity. When engineering a global communications platform, the programming languages and architectural foundations are critical to sustaining growth and reliability.