What’s the difference between SDK and API?

A software development kit (SDK) is a set of platform-specific building tools like debuggers, compilers, and libraries. SDKs bring third-party tools and resources to your environment. In contrast, an application programming interface (API) is a mechanism that enables two software components to communicate with each other using predetermined protocols. You can use APIs to communicate with existing software components and integrate predeveloped functionality in your code. SDKs may include APIs among several other resources for the platform they support. Similarly, you can use SDKs to create new APIs that you can share with others. Both SDKs and APIs make the software development process more efficient and collaborative.

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What are SDKs and APIs?

An SDK provides an integrated platform for you to develop applications from scratch efficiently. It provides the building blocks to shorten the development process. Instead of writing code from scratch, you can use an SDK, which often consists of libraries, compilers, debuggers, code samples, and documentation. An integrated development environment (IDE) is the software environment you use to connect all the tools bundled in the SDK. 

On the other hand, APIs provide you with the means to connect your software with preexisting modules and third-party services. They facilitate interactions between a software application, its internal components, and other platforms. An API abstracts the complexities of exchanging data and helps ensure data integrity in the communication between software components.

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How do developers use SDKs?

As a developer, you can use SDKs to shorten the software development cycle when you build applications or standalone solutions for a specific platform. For example, here are popular types of SDKs.

  • SDKs that include mobile-centered functionality for mobile app development on Android and iOS
  • Cloud platform SDKs for building and deploying cloud applications
  • SDKs specific to a language, framework, or application type for a specific use case

Another example of an SDK is AWS SDK for Python (Boto3), which you can use to integrate Python applications and libraries with AWS services.

When you build complex applications such as natural language processing applications, you can  install an SDK to use available language learning models without rewriting them. 

SDK workflow

When you use an SDK, you want to install it on your computer before you develop an application. During installation, the SDK unpacks all the resources and makes them readily available to you and other developers.

When you build applications, you use the code libraries, debuggers, or other necessary tools provided by the SDK instead of creating them from scratch. For example, you might want to create a secure login page for an ecommerce site. With an SDK, you can import and customize a template from the library with minimal coding.

How do developers use APIs?

APIs expose certain functionalities of their underlying software components. As a developer, you can use APIs to send and receive information to different systems and microservices. As APIs expose their applications to an external environment, you should provide ample security measures when sending a data request.

For example, you can use authorized API keys and authentication tokens to exchange data with a REST API server. REST API is a popular API service that exchanges plain data between web clients and servers. 

API workflows

To use an API, you use the provided function to send a request to the API endpoint. An API endpoint is a server that handles incoming API requests and responds to them. Once the API endpoint validates the requests, it returns the data to you in an agreed structure.

For example, you can use an API to process checkout transactions through an external payment gateway. The API sends the payment details and waits for acknowledgments from the secure payment server.

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Key differences: SDKs vs. APIs

Both SDKs and APIs are important tools in modern software development. Next we discuss the differences between these software building tools. 


An SDK helps you to get started immediately when you work on new software development projects.

Without an SDK, you must assemble the tools you need on your own, which is tedious and requires additional knowledge. For example, imagine that you must choose an IDE that runs specific compilers and debuggers. Once you've set up the development tools, you might need to compare different libraries or frameworks and choose the most suitable combinations to build your applications. 

Meanwhile, APIs are helpful for expanding the capabilities of new and existing applications. You can use APIs to connect a software application with different systems by allowing communication through standardized methods and formats.

It's common for modern applications to use multiple APIs to provide the necessary functionalities to end users. For example, a ridesharing app might use payment APIs, weather APIs, and map APIs to calculate routes and fares with better accuracy. 

Language and platforms 

SDKs are meant to work with a specific programming language or platform. You use different SDKs when you build software applications in different languages. For example, you'd use Java Development Kit (JDK) if you were to develop applications for the Java SE platform. Likewise, you'd download an SDK for a specific social media network if you were to create mobile apps exclusively for that platform. 

Meanwhile, APIs can support one or several languages. This depends on how third-party developers create the APIs. APIs are an extension of software that allows other developers to use specific functions easily. If the software is coded in a language like Java, then the API is available in Java.

However, an API can use a special protocol to exchange information that allows you to perform data requests in different programming languages. For example, you could make API calls to a global mapping service platform with Java, PHP, and Python software codes. 


An SDK contains many tools that allow you to complete a software development project with reduced duration. Therefore, it requires a sizeable installation space in the development environment. Often, you might only use some of the software components contained in the SDK. Depending on the SDK, you might need adequate time to install, set up, and learn how to use the tools.

In contrast, APIs are lightweight software components focused on a specific purpose. APIs don't take up space in your environment, as calling them only requires writing a few lines of code. 

When to use SDKs vs. APIs  

You use APIs when you want to access functionality written by another developer through a suitable interface. You use an SDK when you want platform-specific tools to write code faster. 

Rather than choose between an API or an SDK, you can use both when you develop software. We give some examples below.

Creating a brand-new application

If you're creating a new application, you might choose SDKs. They provide the complete tools for building a platform-specific application or component.

Then, within the code you can call several third-party APIs to develop the related functionality.

Establishing external communication

Modern applications exchange data with other software or microservices to deliver required functionality. In such cases, you may choose APIs to provide a standard communication interface for multiple platforms. An API lets you send and receive data from other developers' services without accessing their codes or understanding the underlying complexity.

Building APIs

You can use SDKs and other APIs to build your own APIs. Sometimes developers share APIs they make for software components they build. They share those APIs with developers, partners, and even the public to use the functionality they've built.

Summary of differences: SDKs vs. APIs





What they are

Set of platform-specific building tools like debuggers, compilers, and libraries.

A mechanism that enables two software components to communicate with each other.


Install SDKs before creating applications.

Apply for API keys to use APIs from third-party providers.


Creates new applications.

Adds third-party functionalities to applications.

Language and platforms

Specific to a particular language and platform.

Cross-platform communication.


Requires installation space for the bundled tools. 

Only require some lines of code to communicate with the external software.

How can AWS support your SDK and API requirements?  

Amazon Web Services (AWS) provides resources and infrastructure that allow you to build, test, and deploy cloud applications effortlessly and at scale. 

Amazon API Gateway is a managed service that lets you publish, manage, and monitor RESTful and WebSocket APIs. It automatically manages traffic, authorization, access control, and other administrative tasks to support API performance and security.

Similarly, AWS provides SDKs for different languages and frameworks to make using AWS services easier in software development. For example, you can use AWS SDK for .NET, AWS SDK for Python (Boto3), and AWS SDK for Ruby when you build web applications on AWS. 

Get started with SDKs and APIs on AWS by creating an AWS account today.