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Hey everyone,
Today, we’re going to break down a common developer question: What’s the difference between an API and an SDK?
These two terms are often used interchangeably, but they actually refer to very different things. And understanding how they work — and when to use them — is essential for any developer building apps, integrations, or systems.
In this article, we’ll walk through what APIs and SDKs are, how they compare, and when to use each — all explained in full sentences and synced with the diagram you see on screen.
Let’s get into it.
What They Are
Let’s start with definitions.
An API, or Application Programming Interface, is a set of rules or protocols that allow one piece of software to communicate with another. It defines the methods and data formats that programs can use to talk to each other.
Think of an API as a menu in a restaurant. It tells you what you can order and how to ask for it — but it doesn’t show you how the food is made.
On the other hand, an SDK, or Software Development Kit, is a full set of tools that help developers build software for a specific platform. It usually includes APIs, libraries, documentation, code samples, and sometimes even debuggers or emulators.
So while APIs define what you can do, SDKs provide everything you need to do it.
Purpose
Let’s now look at the purpose of each.
The purpose of an API is to enable communication between systems. It allows your application to access functionality in another service or platform — like retrieving data from a weather API or posting content to a social media API.
The purpose of an SDK is to help you build applications more easily and efficiently. An SDK gives you tools and ready-to-use components, so you don’t have to start from scratch. For example, a mobile SDK for Android includes APIs, UI components, and tools for building and testing apps.
In short, APIs enable integration. SDKs enable development.
What They Contain
Let’s compare what’s inside.
An API usually contains just the method definitions, endpoints, and request-response formats. It might come with some documentation, but it doesn’t include tools or code to help you use it.
An SDK, on the other hand, is much more comprehensive. It can include one or more APIs, sample code, helper libraries, testing tools, configuration files, and guides.
You can think of the SDK as a toolbox, and the API is just one of the tools inside it.
Usage
Next, let’s look at how each is used.
You use an API when you want to connect to or interact with another system. For example, calling a payment gateway API to charge a customer, or fetching flight data from an airline’s API.
You use an SDK when you are building something — like a mobile app or desktop application — and you need pre-built tools to help you do that. The SDK gives you everything to start coding quickly, including the API.
So, you call an API, but you build with an SDK.
Real-World Example
Let’s look at a real-world example.
Imagine you’re building a mobile app that lets users sign in with Google.
If you use the Google Sign-In API, you’re directly sending requests to Google’s servers and handling the responses manually — managing things like authentication tokens and scopes on your own.
But if you use the Google Sign-In SDK, you get pre-built methods, UI components, and tools that simplify the entire process. It handles the API calls behind the scenes, manages sessions, and even gives you ready-made sign-in buttons.
So, the SDK includes the API — but also much more to make your development faster and easier.
Dependencies
Here’s another important difference: dependencies.
Using an API generally adds minimal overhead. You just need to make requests and process responses — often over HTTP — and it doesn’t require installing large packages.
Using an SDK, however, often means pulling in more dependencies. SDKs may require platform-specific tools, external libraries, or build-time configurations.
That’s not a bad thing — it just means SDKs are heavier but more complete.
Wrap Up
Let’s wrap it all up.
An API defines how software components communicate. It’s like a contract between systems — a set of methods you can call.
An SDK is a full toolkit that helps you build software. It may include one or more APIs, along with sample code, libraries, and documentation to speed up your development.
Use APIs when you want to connect to existing services. Use SDKs when you want to build on top of those services with less effort.
Understanding the difference helps you choose the right approach for your project — and makes you a more confident and capable developer.
If this article helped you understand APIs and SDKs more clearly, give it a like, subscribe to the channel, and let me know what topic you’d like explained next.
Until next time — keep learning, and keep building.
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