As developers, we often come across the terms API and SDK—and they’re sometimes used interchangeably. But while both are powerful tools in a developer’s toolkit, they serve very different purposes. Knowing what each one does and when to use it can make a big difference in how efficiently and effectively you build software.

In this blog, we’ll explore what APIs and SDKs actually are, how they differ, and when to use them—with real-world examples to make things clear.

Let’s break it down.

What is an SDK?

An SDK, or Software Development Kit, is a complete set of tools that developers use to build applications for a specific platform or environment. You can think of it like a toolbox—it comes with everything you need to get started quickly and build more efficiently.

Inside an SDK, you’ll often find:

• APIs to communicate with the platform

• Libraries with reusable code

• Code samples that show you how to implement common tasks

• Frameworks that provide structure to your code

• Documentation to guide you through it all

SDKs help you build applications faster by handling many of the complex or repetitive parts of development for you. Whether you're building an iOS app with the iOS SDK, an Android app with the Android SDK, or working in Java using the JDK (Java Development Kit), SDKs offer a structured, reliable way to get started.

What is an API?

An API, or Application Programming Interface, is more like a contract between different pieces of software. It defines how they talk to each other—what requests you can make, what data you need to send, and what you can expect in return.

Put simply, an API lets different Software systems or components interact without needing to know the inner workings of each other. For example, when a website lets you log in using your Facebook or Google account, it’s using those companies' APIs to verify your identity and pull back basic info.

APIs are everywhere in modern development, making it possible to connect services, fetch data, and perform actions in a consistent, reliable way.

What Makes Up an SDK?

A Software Development Kit (SDK) contains multiple components that help developers build software applications. Here are the main ones:

1. Libraries – Prewritten code that handles common tasks.

2. Frameworks – Structure and tools for building your app.

3. APIs – So you can interact with the platform or service.

4. Documentation – Instructions, examples, and guidelines.

5. Tools – Such as compilers, emulators, debuggers, etc.

6. IDE (sometimes) – An all-in-one coding environment, depending on the SDK.

Not every SDK includes all of these, but the goal is always the same: to simplify and speed up the development process for a specific platform or service.

What Makes Up an API?

An Application Programming Interface (API) consist of several key components that define how software systems communicate. Here are some of the key ones:

1. Endpoints – URLs that you send requests to.

2. HTTP Methods – Such as GET, POST, PUT, DELETE, etc.

3. Request/Response Format – Commonly JSON or XML.

4. Parameters – Extra information passed with your request.

5. Headers – Metadata like auth tokens or content types.

6. Error Messages – Responses when something goes wrong.

7. Rate Limiting – Limits to how many requests you can make.

8. Authentication & Authorization – API keys, tokens, or OAuth flows.

9. Documentation – Guides and reference info for using the API properly.

These elements make it easy for developers to integrate third-party features or services into their applications.

Types of SDKs

SDKs come in various types depending on their specific purpose, the platform they are designed for, and the programming language they support. Here are some of the most common:

• Platform SDKs – For building on specific operating systems (e.g., Android SDK, iOS SDK).

• Web SDKs – For integrating or building web apps (e.g., Facebook JavaScript SDK).

• Game SDKs – Tools for building games (e.g., Unity, Unreal Engine).

• Hardware SDKs – For interacting with physical devices (e.g., IoT or printer SDKs).

• Cloud SDKs – For managing and using cloud services (e.g., AWS, Azure, Google Cloud).

• Payment SDKs – To integrate payment systems (e.g., Stripe, Razorpay).

• Advertising SDKs – To serve and manage ads in your app (e.g., AdMob).

• Analytics SDKs – To track user behavior (e.g., Google Analytics).

• Social Media SDKs – For login and sharing features (e.g., Facebook SDK, Twitter Kit).

• VR/AR SDKs – For building immersive experiences (e.g., ARKit, ARCore).

• Video SDKs – For live streaming or real-time video (e.g., Dyte, Agora).

Types of APIs

APIs come in various types, each serving a different purpose. Here are some of the most common types:

1. Web APIs – The most common; communicate over HTTP.

2. REST APIs – Follow the REST architecture; simple, stateless, and use standard HTTP methods.

3. SOAP APIs – Use XML and a strict protocol structure.

4. GraphQL APIs – Let clients request exactly the data they need.

5. gRPC APIs – High-performance, binary-based APIs built with Protocol Buffers.

6. Real-Time APIs – Keep connections open for live data (e.g., WebSockets).

7. Hardware APIs – Allow interaction with hardware components.

8. Library APIs – Expose functionality from programming libraries.

9. OS APIs – Provide system-level access to resources and services (e.g., Windows API).

Each type serves a different purpose, and you’ll often see several used together in complex systems.

Comparing SDK vs API

When to use an SDK vs an API?

SDKs and APIs both play important roles in software development, but they serve different purposes—and knowing when to use which one can really make your work easier.

You’d typically go for an SDK when:

1. You're building something for a specific platform: For example, Android or iOS. SDKs are designed for this—they include the tools, libraries, and everything else you need to get started.

2. You want a full toolkit: SDKs usually come packed with sample code, documentation, and even an IDE sometimes. It’s like getting a starter kit that saves time and simplifies the process.

3. You’re dealing with complex stuff: If your project involves multiple API calls or detailed workflows, SDKs can make life easier by handling much of that complexity for you.

On the other hand, you'd use an API when:

1. You need to connect with another service: APIs are great for things like sending data to Twitter, processing payments, or accessing third-party services.

2. You just need a specific function: If you only need to do one thing—like send an email or verify a user—an API is lightweight and straightforward.

3. You want more control: If you’re working with a custom setup or unsupported language, APIs give you the flexibility to build things your way.

Honestly, in most real-world projects, you’ll probably use both. The SDK might handle the core development, while APIs let you plug into external tools or services whenever needed.

Conclusion

At the end of the day, it’s not about choosing one over the other—it’s about choosing what works best for your project. SDKs are great when you want a complete toolkit and smoother development for a specific platform. APIs shine when you need flexibility, quick integration, or specific features. The better you understand the difference, the better decisions you'll make as a developer.

"I hope this breakdown makes it easier for you to choose between an SDK and an API for your next project. From my experience, understanding these tools can really speed up development and reduce headaches.

If you’re new to development or just want to share your thoughts, feel free to comment below — I’d love to hear your stories and tips!”