Glossary
SDK (Software Development Kit)
A packaged set of libraries, APIs, tools, sample code and documentation for building on a specific platform or service. An SDK gives you working building blocks instead of a raw interface.
General definition
SDK (Software Development Kit) is the term for the bundle a platform vendor gives developers so they can build on that platform quickly. A typical SDK contains client libraries in one or more programming languages, an API wrapper that hides raw HTTP or socket calls, command-line tools, sample applications, type definitions and documentation. Mobile platforms ship SDKs (the iOS SDK, the Android SDK); so do cloud services, payment providers and messaging platforms.
The words SDK, API and library overlap, and the distinctions matter when you compare vendors:
- API: the interface itself, the set of endpoints or function signatures a service exposes. You can call an API with nothing but an HTTP client.
- Library: a single piece of reusable code, for example an npm package that renders a chat window. A library may be one part of an SDK.
- SDK: the whole kit: libraries, tooling, samples and docs, usually versioned and supported together as one product.
- Framework: a structure that calls your code rather than the other way round (React, Next.js, Android Jetpack). SDKs are usually written to fit inside a framework.
A good SDK is judged by how much of the hard work it absorbs. For real-time messaging that means connection handling and reconnection, authentication tokens, offline caching, push registration and prebuilt UI. It is also judged by openness: whether the source is available, whether it locks you to one hosting model, and how it is versioned. Semantic or calendar versioning, a changelog and a deprecation policy are signs of a kit you can build a product on.
In the Ethora ecosystem
Ethora ships its platform as a set of SDKs rather than a bare API. The Chat SDK covers React and web (the @ethora/chat-component package on npm), React Native (@ethora/chat-component-rn), native iOS in Swift and native Android in Kotlin, written in TypeScript or the platform language, with React 19 support on the web side. The AI SDK adds agents, RAG over a knowledge base, tool calling and multi-agent rooms on top of the same backend.
Around the SDKs sit the developer tools: the @ethora/setup CLI for project scaffolding, an MCP server (@ethora/mcp-server on npm and the MCP registry) so Claude and other MCP clients can create apps, users and rooms, sample apps, public docs and monthly calendar-versioned releases with notes on the blog. The server side is open source, and the same kit works against the managed cloud, a dedicated server in your own cloud account, or a self-hosted Docker deployment.
