WhatsApp is one of the most popular messaging apps in the world, with over 2 billion users. The app allows users to send messages, photos, videos, documents and make voice and video calls for free. WhatsApp is available for smartphones as well as PCs through WhatsApp Web.
WhatsApp Web provides the same features as the mobile app, enabling users to seamlessly continue conversations from their computer browser. But how does WhatsApp Web work and what technology does it use to sync messages and data across devices? Let’s take a closer look.
How WhatsApp Web Works
WhatsApp Web is an extension of the WhatsApp account on your phone. To use WhatsApp Web, users need to scan a QR code from the WhatsApp desktop website using their phone to link the desktop browser to their account.
Once linked, WhatsApp Web syncs all messages, contacts and data from the phone. This allows users to continue messaging on the desktop without interrupting the conversation thread on their phone. New messages sent from the desktop are synced back to the phone as well.
End-to-End Encryption
WhatsApp applies end-to-end encryption for all communications to keep user data secure. The encryption ensures only the sender and recipient can read the messages, not even WhatsApp itself. This encryption extends to WhatsApp Web as well to protect chat data and privacy.
Real-time Syncing
WhatsApp Web provides real-time syncing of messages across the phone client and desktop browser. This instant sync is enabled by the underlying WebSocket technology.
Core Technical Components
WhatsApp Web relies on several key technical components to enable real-time messaging and data sync from the mobile device to the browser. These include:
WebSocket Protocol
WhatsApp Web uses the WebSocket protocol to enable real-time, bidirectional communication between the phone client and browser. This allows instant syncing of messages sent and received on either device.
WebSocket provides full duplex communication between the client and server over a single TCP connection. This makes it much more efficient compared to HTTP polling or long-polling techniques used traditionally.
Encrypted Data Channel
WhatsApp establishes an encrypted data channel between the mobile app and browser for syncing messages and data. This ensures all communications are secure and end-to-end encrypted.
QR Code Scanning
WhatsApp uses the phone’s camera to scan the QR code displayed on the desktop browser. This QR code contains the keys to encrypt the communication channel. Scanning the code links the desktop browser session to the account on the phone.
Contact and Message Sync
Once connected, the desktop browser has access to all message threads, contacts and chat history from the phone. New messages and updates made on either device are synced in real-time across both platforms.
Notifications and Call Handling
Notifications for new messages and calls continue to be handled by the phone. For calls, the desktop browser sends call requests to the mobile client to initiate and handle the call.
Front-end Technologies
In addition to the core communication technologies, WhatsApp Web also relies on various front-end frameworks and libraries:
ReactJS
WhatsApp Web’s user interface is built using the React JavaScript framework. React allows creation of fast, interactive UIs that can smoothly sync data in real-time across platforms.
TypeScript
WhatsApp Web frontend code is written in TypeScript. TypeScript extends JavaScript by adding static typing that allows for better tooling and large codebase management.
Flux Architecture
WhatsApp follows the Flux architecture for building the frontend. Flux promotes unidirectional data flow between UI components, which helps manage updates across the desktop and mobile apps.
Bootstrap
WhatsApp Web uses the Bootstrap framework for responsive web design. Bootstrap provides CSS and JavaScript tools for building device-agnostic UIs that adapt to desktop or mobile screens.
Back-end Infrastructure
Supporting WhatsApp’s over 1 billion daily active users requires significant back-end infrastructure. Key components include:
Erlang VM
WhatsApp runs on the Erlang virtual machine. Erlang allows building massively scalable, real-time messaging systems that provide high availability.
Custom Erlang Processes
WhatsApp uses thousands of custom Erlang processes to handle events like messaging, notifications, user presence, and more in real-time.
Distributed Servers
WhatsApp operates tens of thousands of distributed Erlang nodes on servers across data centers around the world to achieve scale and reliability.
Caching Servers
WhatsApp relies heavily on caching with servers like Redis and Kafka to reduce database loads and optimize performance.
Load Balancers
Load balancers distribute connection requests across WhatsApp’s thousands of application servers. This helps manage massive traffic spikes and ensure uptime.
Database Technologies
WhatsApp uses a range of database solutions to store and manage the vast amounts of user data as well as application data for enabling communications. Key databases powering WhatsApp’s service include:
MySQL
WhatsApp uses MySQL to store critical user data like profiles, contacts and chat logs. MySQL provides a fast, reliable and scalable relational database for WhatsApp’s core needs.
Redis
Redis offers ultra-fast in-memory data storage and retrieval to power WhatApp’s real-time messaging capabilities and presence system. It also acts as a cache and message broker.
HBase
WhatsApp leverages Apache HBase for its distributed NoSQL database needs. HBase is built on HDFS and handles massive workloads across thousands of commodity servers.
Cassandra
WhatsApp uses Cassandra for its scalable Wide Column Store system to handle high write throughput at low latency. This enables durably storing enormous volumes of time series data.
Kafka
Kafka acts as a distributed streaming platform to build and manage WhatsApp’s real-time pipelines for messaging and data synchronization.
Multimedia Content Delivery
WhatsApp needs to deliver vast amounts of multimedia content like images, videos and voice messages across its network. Key technologies that enable this include:
Media Storage on S3
WhatsApp stores billions of images and videos sent daily by users on Amazon’s S3 service. S3 provides secure, durable object storage built for scale.
Content Delivery Networks
WhatsApp leverages CDNs like Fastly to cache and deliver multimedia content globally and optimize performance. Local CDN caches minimize latency.
WebRTC for Voice/Video Calls
WhatsApp uses the WebRTC protocol to enable real-time voice and video calling right within application. WebRTC provides built-in audio, video and data streaming between peers.
Media Codecs
WhatsApp utilizes audio and video codecs like Opus and H.264 to compress and transmit voice notes, voice calls and video chats between users efficiently across the network.
Security Protections
As a communications platform carrying sensitive user data, security is a critical priority for WhatsApp. The service leverages various technologies to achieve privacy and security:
Transport Layer Encryption
WhatsApp secures all network communication with Transport Layer Security (TLS) and ensures HTTP Strict Transport Security (HSTS) to prevent eavesdropping.
End-to-End Encryption
WhatsApp implements end-to-end encryption using the Signal protocol to secure all texts, media and calls. Encryption keys are only stored on user devices.
| Encryption Type | Description |
|---|---|
| Asymmetric Encryption | Uses public/private key pairs to establish secure connections between devices |
| Symmetric Encryption | Applies session keys for faster encryption of message contents |
Code Obfuscation
WhatsApp obfuscates its Android and iOS app code to prevent tampering and unauthorized attempts to bypass encryptions.
Digital Signatures
WhatsApp digitally signs updates and SMS messages to certify their origin and integrity. This prevents man-in-the-middle attacks.
Local Storage on Devices
To ensure fast, responsive service for users, WhatsApp leverages storage on user devices:
Async Storage on React Native
For its React Native apps, WhatsApp uses the Async Storage API to store data like authentication tokens and user preferences locally.
SQLite Databases
WhatsApp apps use SQLite databases on Android and iOS to cache and query user data like messages and contacts locally on the device.
File System Storage
Multimedia exchanged by users like images, videos and documents is stored locally on the device file system under encrypted folders.
Keystore for Credentials
The app stores user credentials like encryption keys securely on the phone’s keystore. Access requires user authentication via fingerprint or passcode.
Testing and Deployment Tools
Given WhatsApp’s enormous codebase and userbase, a sophisticated testing and deployment pipeline is required. Key tools include:
ProGuard
WhatsApp uses ProGuard to shrink, optimize, obfuscate and preverify its Android code through the build process to cut apk size.
Buck
For its React Native apps, WhatsApp utilizes the Buck build system to build and test code faster by leveraging caching and parallelization.
Git
WhatsApp engineers rely heavily on Git for version control and collaboration during development while shipping code changes.
CI/CD Pipelines
WhatsApp has implemented robust continuous integration and continuous delivery pipelines to automate building, testing and releasing app updates.
Crash Reporting
WhatsApp uses crash reporting tools like Crashlytics to monitor app crashes in real-time and fix critical bugs faster.
Staged Rollouts
New WhatsApp versions are slowly rolled out to subsets of users to control quality and monitor for issues before wider release.
Conclusion
WhatsApp Web relies on a sophisticated stack of technologies across the front-end, backend, databases, security, testing and operations to deliver its messaging service at scale to over a billion daily users. The use of Erlang VM for real-time performance, React for building fluid UIs, WebSockets for syncing data across devices, end-to-end encryption for security and scalable databases like Kafka and Cassandra enables WhatsApp Web to provide a seamlessly fast and secure messaging experience across platforms.
Continuous development and refinement of WhatsApp’s core technology stack allows the service to maintain its leadership as one of the most reliable and high-performance messaging platforms globally. WhatsApp’s focus on speed, security and simplicity has led to massive adoption across both emerging and developed markets worldwide.
While the underlying protocols and components may evolve, WhatsApp’s adherence to innovative engineering, user-centric design and robust infrastructure provides a solid technical foundation for the platform to scale and meet the needs of the next billion users in the years to come.