What are Chat APIs? Messaging Apps

With new apps emerging daily, real-time chat is key for competitive online experiences. Chat APIs simplify adding chat without in-house development. This guide covers their benefits, selection, and implementation.

What is a chat API?

A chat API is an application programming interface that provides access to a cloud-based infrastructure with the features to build live chat that scale. Chat APIs are usually offered as a service, and they can be easily embedded in an application with the use of a chat SDK (Software Development Kit).

Unlike messaging APIs that focus on SMS/MMS, chat APIs enable real-time communication using protocols like HTTPS, XMPP, or MQTT for seamless integration. They structure data, often in JSON, for seamless cross-platform integration. However, some systems use Protocol Buffers (protobuf) or other serialization methods for optimized performance and efficiency.

While messaging APIs primarily handle one-way or asynchronous SMS/MMS delivery, chat APIs support instant, interactive communication, including typing indicators, read receipts, and presence detection. Some platforms bridge the gap by offering SMS messaging and real-time chat, enabling businesses to provide a unified communication experience.

Additionally, the best chat APIs are just one part of a larger real-time communication platform. This means that the service you initially use for chat will facilitate expansion to new features, like SMS, push notifications, video calling, and chatbots.

You can use a chat API in almost any context. Whether building an app or a web-based experience, you can use a chat API to build engaging, responsive chat for many use cases.

Types of Chat API

A chat API enables seamless live chat integration for various use cases, driving business growth through real-time customer communication.

Video Chat API

Video chat describes visual, remote communication between two or more parties, each equipped with a camera and microphone to see and hear the other. Beyond supporting in-app chat messaging, PubNub acts as a signaling layer to orchestrate video and voice calls of any size and to underpin live-streaming, large-audience events. PubNub also allows you to log chat events around the call to capture complete details and histories for later use.

Chatbot API

A chatbot is a software application used to conduct an online chat conversation via text or text-to-speech, in lieu of providing direct contact with a live human agent. It’s commonly used to allow people to quickly ask questions and provide support for a wide range of use cases (online orders, customer support, rideshare and delivery apps) without the need for users to open another application. 

Chat API for Website

A Chat API is a collection of programmable building blocks that can be used to provide real-time chat features for in-app chat, or for chat on a website. Companies use a Chat API to engage new customers in the sales process or to enhance relationships with existing customers by offering direct live support. An organization may also create an internal collaborative chat environment for employees to improve productivity across different departments. Another use case that has become popular is to provide mass audience engagement during live events in the form of a streaming chat window (e.g. for spectators of competitive eSports).

API for chat application

A chat application should facilitate conversations that feel natural and comfortable for users. This is something that consumers now expect from a chat experience. Chat APIs provide these user-friendly features to ensure that your users' needs are met. In-app chat APIs are usually offered as a service by a third-party PaaS cloud provider and can be easily embedded in an application by following the respective chat API documentation or with the use of a Chat SDK (Software Development Kit).

HIPAA Compliant Chat API

HIPAA-compliant chat APIs meet strict privacy standards, including end-to-end encryption, data storage protection, and access controls to prevent unauthorized access to protected health information (PHI).

They also include features like audit trails for tracking data access and usage, user authentication, and secure communication channels. This ensures patients can share PHI, receive push notifications, and enjoy real-time communication with their healthcare providers while maintaining privacy and compliance.

PubNub chat API service

The best chat service should meet your app's foundation needs. A production-ready messaging API is more than a transport layer—it's a critical service driving user engagement. Whether you're building for healthcare, gaming, e-commerce, or social platforms, the chat layer must be as reliable and scalable as your core tech stack.

Core Functional Capabilities

To support a modern, production-grade messaging experience, your Messaging API should provide the following baseline capabilities:

• 1:1 or Private Messaging: Support low-latency, secure message delivery between two authenticated users, including typing indicators, message read receipts, and end-to-end encryption (E2EE) for privacy-critical use cases.
• Group Chat Support: Enable persistent and dynamic chat rooms that support a vast number of participants. Features should include user access control (roles/permissions), message threading, secured media sharing, and moderation tools for scalable community management.
• User Presence and Activity Indicators: Provide real-time visibility into user status—online, offline, idle—using a scalable presence model, typically via pub/sub mechanics with efficient diffing and throttling strategies to avoid excessive bandwidth usage.
• Push Notification Integration: Native support for APNs, FCM, and web push services to deliver timely notifications when users are offline, with deep linking to resume chat sessions and intelligent batching to optimize delivery and engagement.
• Persistent Chat History: Durable message storage with configurable TTL (time-to-live) policies, conversation searchability, and audit-compliant logging. The system should support pagination, lazy loading, and message pinning/bookmarking.

Architectural & Operational Requirements

At a production scale, a messaging API must be engineered to handle complex operational and architectural demands:

• High Availability and Fault Tolerance: Distributed architecture across multiple regions and availability zones to eliminate single points of failure. Built-in failover strategies and message replay mechanisms ensure continuity during network disruptions.
• Massive Concurrency Support: Ability to support millions of concurrent users across channels using efficient event distribution models (e.g., fan-out-on-write or hybrid pub/sub). Horizontal scalability via sharded message brokers or event buses is essential.
• Low Latency Delivery: Sub-100ms message delivery targets across global regions, with local edge relays, aggressive TCP connection reuse, and adaptive retry/backoff policies to account for unreliable client networks.
• Security and Data Compliance: TLS encryption in transit, optional E2EE, per-message access policies, rate limiting, and activity logging. Compliance with regulations such as GDPR, HIPAA, or SOC 2.
• Extensibility via Hooks and Events: Webhooks and server-side event processing to integrate business logic (e.g., moderation, analytics, CRM updates) with real-time triggers such as "onMessageSent", "onUserJoined", or "onChannelCreated".
• Multi-Platform SDK Support: SDKs or client libraries for iOS, Android, Web, Unity, and backend frameworks (Node.js, Python, etc.), with feature parity across platforms and easy customizability to align with UI/UX requirements.
• Observability and Monitoring: Integrated dashboards, metrics (latency, throughput, error rates), distributed tracing, and alerting hooks (via Prometheus/Grafana, Datadog, or similar). Log correlation with external services for end-to-end debugging.

How PubNub scales up live chat API

A chat API handles concurrency and scalability using distributed architectures and load-balancing techniques. It scales horizontally, distributing traffic across multiple servers or containers to handle high message volumes. Asynchronous processing, often via message queues or event-driven systems, ensures that chat messages are processed efficiently without blocking other operations. To manage concurrency, the API uses techniques like sharding and replication to ensure consistent performance even during surges in usage or large numbers of simultaneous users.

Who uses PubNub chat API?

PubNub’s chat APIs make it easy to build fully-featured chat at a lower cost and with a shorter time to market. Because PubNub offers APIs designed for full customization and integrations with best-in-class services, it saves our customers time and cost not having to build from scratch. This also allows developers to concentrate their efforts on building an engaging chat experience that aligns with their core product offering. 

Here’s a look at how to use a chat API:

• Virtual Events: Stream chat during live events to give users the ability to engage with audience members and react to messages using emojis, keeping conversations lively and interactive. 
• Telemedicine: Private chat between doctors and patients enhances virtual care by ensuring seamless communication for scheduling, virtual waiting rooms, consultations, and when sharing electronic private health information (ePHI).  
• Gaming: Live chat for online games creates a natural way for players to form bonds while competing side-by-side with one another. Plus, you can add live scores and leaderboards alongside your chat for deeper user engagement. 
• Support: Chat between agents and customers are pushed in real time to resolve requests quickly, which helps improve efficiency and customer satisfaction. 
• Marketplaces: Chat between buyers and sellers builds long-lasting customer relationships by continuously engaging with consumers, notifying them of real-time pricing, updates, and relevant offers that are customized to their shopping needs. 
• Collaboration: Chat for team communication at the workplace facilitates impactful collaboration where users can work together simultaneously in Virtual Spaces to increase productivity. 
• Social: Chat with your online community in a way that feels organic. Whether an audience is interacting during a virtual concert, those in a fitness class are cheering on each other, or fans are celebrating a sports event, you can enable these memorable connections through chat. 

PubNub Chat API documentation: What you’ll find

Ready to add chat APIs but aren’t sure where to start? We’ve compiled a list of essential resources to give businesses the guidance needed to strategically build scalable chat apps faster. 

Find answers, read up on the best practices, and build features that align with your customers needs and business goals.

• PubNub Docs: Explore our documentation and technical resources.
• In-App Chat:See how you can build engaging in-app chat experiences at any scale.
• PubNub Platform: Read about our core features such as Presence, Functions, and Access Control.  
• PubNub for Developers:Browse our product tour, demos, and tutorials.
• Blog: Learn about new PubNub releases, industry trends, and app development tips. 
• How-To’s: Read our collection of guides to help you understand key concepts of building applications or architecting on PubNub. 
• Demos: Visit our demos to get an idea of what you can build. 
• Integrations: Discover how to integrate best-in-class third party services directly into your app.
• Guides: Everything you need to know about building scalable real-time applications. 
• Developer Paths: All the resources you need to quickly and easily build chat, virtual events, IoT, and more. 

Getting Started with PubNub Chat API

Whether working or socializing, chat has become a vital part of our everyday communication. A chat API service enables you to easily and quickly incorporate chat into your product for a more enriching and engaging user experience. 

At PubNub, we take care of the scalability and reliability so you can focus on what matters: your customers.

If you’re ready to enhance your app with chat APIs, create a free account

We’ll get you up and running with our APIs, so you can build chat that your users will love.

Not quite ready yet? Check out our interactive Chat demo, built entirely with the PubNub Chat SDK.