January 11, 2021

What is the difference between an API and an SDK?

Shane Bird

There is often confusion between what an SDK and an API are, and why an app would want to integrate either of these third-party softwares. Many people in the tech industry have a rather vague or incorrect idea regarding APIs and SDKs, and it is common for the 2 to get mixed together. One of the main reasons for this confusion is because SDKs usually contain APIs but, not vice versa. To understand the difference in-depth, let's start by defining the two terms and later jump into their differentiation.

What is an API?

API is an acronym for Application Programming Interface. An API is a software intermediary that allows two applications to communicate with each other.

Let’s say you make a request to an API for a list of products in JSON format. Typically, the server will check if you have the proper credentials, and if you do, then gives you the list of products you requested.

In layman's terms, an API is a messenger that delivers your request to the provider that you're requesting it from and then responds to you.

An API defines the correct way for a developer to request services from an application and expose data within different contexts and across multiple channels. Therefore, a good API makes it easier to develop a program by providing the building blocks.

Why are APIs important?

● APIs help developers to add new features to their apps easily. Rather than building something from scratch, a developer can access a useful API to save them development time and ensure that key functionality works effectively.

● By using APIs, developers help reduce fragmentation across the Internet and improve navigation through an interconnected ecosystem of sites, platforms and mobile apps.

● Finally, APIs can also help stitch the internet and mobile app economy together on behalf of users. They underpin essential online behaviours – such as share buttons or social login options. Even using mapping data in e-commerce apps requires an API, and as such, APIs have become essential to users.

API Example

Ever wondered how a travel booking website can aggregate thousands of flights and destinations and show the cheapest option? Usually, the answer is to use third-party APIs to collect flight and hotel availability from providers. Similarly, if you book through one of these services, they will use the API to confirm the itinerary with the provider from them.

APIs are great for travel services because they allow machines to easily and automatically exchange data and requests (in this case, travel availability and reservation requests). Without using the API , the staff who booked the service had to manually email the airline or hotel to learn about its availability. Then, after the provider receives the email, they must confirm with the traveller. By the time the travel agent sends an email to the provider again to confirm the trip, it may no longer be available!

What is an SDK?

A Software Development Kit (SDK) is typically a set of tools that can be used to create and develop Applications. In general, an SDK refers to a full-suite software module that includes one or more libraries or APIs, processes, programming tools, sample code, documentation as well as guides that developers can use and integrate into their apps.

Although SDKs are commonly used for mobile applications, they can also be used on websites and other digital platforms too.

A common analogy that can better explain SDKs is to compare them with a model car kit. The kit contains the necessary items such as model parts, instructions, glue, and other tools needed to put them together.

Why are SDKs important?

Without an SDK, a lot of this pre-built functionality would have to be made from scratch. SDKs let you create new tools efficiently and make the process easier for anyone integrating them as everything is pre-built.

SDK Example

SDKs can be used in cases as simple as the implementation of one or more application programming interfaces (APIs) in the form of some libraries to interface to a particular programming language or to include advanced hardware that can communicate with an appropriate embedded system. SDKs are widely associated with mobile native apps, it is possible to make use of them in connection with websites and other digital platforms. A mobile SDK is used for building a mobile application for iOS and Android devices.

For example, in the majority of mobile apps, a user will need to login and most apps use oAuth logins from the likes Facebook, Twitter and Google. All three companies provide their own SDKs for mobile applications, that allows the developer to easily make the requests necessary to initiate the functionality within, in this instance to authenticate the user.

The Difference between APIs and SDKs?

An application programming interface (API) and software development kit (SDK) both play an important role in the software development process. As the name implies, an API acts as an interface between different applications or platforms and helps various software programmes interact. They usually contain specifications that can be used to interface between different software programmes. On the other hand, the SDK consists of development tools and pre-written code that developers can use to build their applications. The SDK usually reduces the workload and time required for developers to write their unique code to build software applications.

APIs may contain routines, data structures, protocols, and object class specifications to facilitate interaction between different programmes. To facilitate interaction with embedded systems, the SDK usually consists of files or APIs in the form of complex hardware. The SDK plays a vital role in eliminating work duplication and saving developers the time to create new software applications. An API usually includes a set of rules and specifications, and software programmes will follow these rules and specifications to facilitate easy interaction.

The API does not have any written sample code but includes a detailed description of function calls and function prototypes' behaviour. The SDK consists of sample programmes, technical descriptions, utility programmes, and debugging tools for programmers to integrate into the development of applications, thereby saving a lot of time and effort.

When to use SDK and when to use an API?

Developers always use the SDK when building applications. Besides, there are SDKs specifically designed for specific platforms, for example, an Android SDK would be specific to android applications. The API is used to communicate with external applications or platforms through various methods and protocols.

In short, when developing any software application, engineers will use the SDK. When you need to communicate with other third-party service providers (application/platform), you will use the API integration. Which may perhaps be part of the SDK.

Summary

To summarise, APIs act as an interface for different applications to communicate with one another, while an SDK provides a set of tools and utilities needed to develop software programmes. API only contains specifications and descriptions about functions, while SDK contains API, sample code, technical documents, tools, and utilities. The API describes the parameter types and return value types to be provided to the function, and the SDK contains libraries that can be used to develop software applications.

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