What is SDK and the Difference Between SDK and API?

APIs represent the communication between different software components, while SDKs represent an entire toolkit that contains APIs for a specific task.

A developer ecosystem functions on two foundational tools, an SDK and an API. Today, it is critical to understand the fundamental differences as the developer community uses both extensively in the modern software development process.

The development landscape is fueled by these two ingredients. SDKs and APIs are the key drivers for the implementation of third-party APIs and web communication.

Essentially, both the SDK and API serve well to improve your application’s overall functionality and performance. However, to enhance the experience for both in-house teams and end-users, it is inevitable to learn how these tools operate, how they are different, and how they aid in the software development process.

Let’s take a closer look at each one of these tools.

What is an SDK?

SDK is an acronym for “Software Development Kit”, also referred to as ‘devkit’. SDK is defined by a set of software building tools that are specific to platforms. These tools include debuggers, compilers, code libraries (i.e., framework), or routines and subroutines targeted towards an operating system.

The building blocks of a typical SDK include the following:

• Debugger: A debugger enables developers to identify and correct errors in the program code.
• Compiler: A compiler is a program that processes programming language statements and translates them into machine understandable language or “code” used by the processor.
• Code samples disclose programming tasks or scenarios that give a clearer picture of an application or web page.
• Routines & subroutines: A routine or subroutine is a method, function, procedure, subprogram, or code that can be called and executed anywhere in the entire program code. For example, the save file option is executed via a routine.
• Code library: A code library allows developers to use existing resources (e.g., code sequences) rather than reinventing them.
• Testing and analytic tools: These tools rate the application’s performance in a testing and production environment.
• Documentation: Developers refer to documented instructions (as needed) during the development process.

Generally, an SDK at least has one API in its kitty, as applications cannot interact, relay, function, or collaborate without the API.

How does an SDK Work?

SDKs provide a suite of tools necessary for developers to build software applications with ease.

For example, Facebook provides SDK for Google’s Android and Apple’s iOS. These SDKs act as open-source libraries that help integrate Facebook into your Android or iOS app. Besides, Microsoft offers .NET framework SDK for large-scale applications. It contains samples, tools, and libraries essential to develop applications for Windows.

Now that you are familiar with the nitty-gritty of SDKs let’s understand the working of SDKs.

• Initially, you purchase, download, and install the requisite “kit” for your platform. This may cover downloading files that include constituent parts, instruction sets, and examples.
• Next, you may access all the necessary tools, integrated development environment (IDE) to develop a new application. Following which the developers can start coding their applications. A compiler’s role becomes evident in this stage.
• Finally, you can use instructions, documentation, code samples, and analytics tools to test the new application.

Once you complete these steps, you can start your SDK journey.

Types of SDKs

Web and mobile app developments run on the premise of SDKs. Let’s look at some of the common SDK types.

• Platform SDKs: These SDKs are the key components necessary for app development for any platform. For example, the Windows 10 SDK is used to develop Windows 10 Store apps.
• Extension SDKs: These are optional SDKs that are used to extend and customize the development environment. However, they are not a must for developing apps for a particular platform.
• Programming language-specific SDKs: Such SDKs are used to develop programs in specific languages. For example, Java Developer Kit (JDK) is used for developing applications using the Java programming language.
• Analytics SDKs: These SDKs collect data such as user behaviors, actions, etc. For example, Google’s Analytics SDK.
• Monetization SDKs: Such SDKs are used by developers to deploy advertisements that pop out of the existing apps. They are put in place with the sole purpose of generating revenue.

SDK Benefits

SDKs present several benefits for the developer community. Primarily, they do not have to toil hard to develop applications with efficient use of software development kits.

• Access premade parts: SDK provides easy access to premade parts, thereby cutting down the time spent in software development. For example, Android map SDK enables you to configure and deploy various location services in your app. The SDK provides easy access to constituent parts and collates them together in the app (e.g., location coordinates such as longitude, latitude, services within a specific location).
• Seamless integrations: SDKs offer smoother integrations with different software and applications. They also provide direct access to required information via proper documentation.
• Provide shortcuts to developers: SDKs allow developers to reuse code sequences as it shortens the development cycle. This gives developers ample time to focus on critical tasks.
• In-built support: SDKs are enabled with in-built code expertise (support), including complete documentation. Thus, developers need not lookout for experts in the domain to get their queries resolved.
• Affordability: The factors mentioned above help negate excessive expenditures incurred in software development and post-deployment phases.

Let’s now jump to the intermediary API component.

What is an API?

API is an acronym for ‘Application Programming Interface’. It elaborates a set of rules using which the platforms, devices, or applications connect and communicate with each other. API can either be a part of an SDK or exist independently. In both scenarios, it establishes systemic synchronicity between diverse applications.

The developers maximize the benefit of non-free (proprietary) or cloud-based software to build effective APIs. They may then leverage services that users can access via the built APIs.

API is analogous to an agreement between two parties. It offers instant information exchange along with guidelines on how the information should be communicated.

Some APIs are known to provide ‘interface’, hence ‘API’ and ‘interface’ are loosely regarded as the same entities.

Key components

API has two key components:

• Technical specifications: Specifications for an API  refer to the information relating to the protocols for API integration (i.e., with other platforms, applications). They need to be well documented to ensure effective usage of the API.
• The interface: Interface provides a pathway for accessing APIs. It can be accessed with a keyword if it’s a web API or via a separate interface.

Let’s now dive into how a typical API works.

How does an API Work?

APIs allow smooth dialogue between various sets of applications.

Consider an example where you already have a grocery selling app where your users can search for and buy groceries online. Your app already provides this service. Now, let’s say the users also want to look for grocery centers at a specific location within a city. In such a case, you can integrate your app with established grocery service providers’ operating in the city. By deploying geolocation API, you would allow users to look for grocery centers without worrying about a separate geo-location application.

From a technical point of view, an API call follows the below steps:

• An application user initiates the task from your app by creating a request.
• The API relays the request by making a call to the webserver. The API is aware of where to send the request as the request typically is targeted to reach the API endpoint. The server URL defines the endpoint.
• Lastly, the task is accomplished as the database, or third-party application provides the requested service.

Types of API

REST (Representational State Transfer): REST APIs are one of the most popular API types where the API needs to adhere to a set of principles such as:

• Client-server architecture: Changes made on the server shouldn’t affect the client
• Communication between client and server via HTTP, CRUD (Create, Read, Update, Delete) and JSON.
• Statelessness: There is no storage of the client’s state on the server between any two requests.

REST is usually used to transfer data. For example, Facebook API is used to get a Facebook user’s name, location, and profile picture into another app.

RPC (Remote Procedure Call): This is used to execute code on another system. In contrast to REST, where the client only requests data, RPC calls methods. The requests can be sent in XML or JSON formats and are called XML-RPC and JSON-RPCs. The sender of the request expects a response from the other system after the method is executed.

For example, a payment gateway API authenticates a credit card number (executes code at its end) and sends a success or failure response to the calling app.

SOAP (Simple Object Access Protocol) APIs: They are web-based APIs used in cases that require enhanced data privacy and security. They can communicate over web-based protocols such as HTTP, SMTP, TCP/IP, etc.

SOAP is a set of protocols, whereas REST is an architectural model. This makes it possible to create RESTful APIs using SOAP-based protocols.

API Benefits

APIs are beneficial to both groups, ordinary users and development professionals. Developers can connect with the business stakeholders to update agency systems and expand the agency’s business potential.

Although the benefits may bring in the developer perspective, APIs amplify both the developer experience and end-user experience. Let’s glance through some of the benefits offered by APIs.

• Integration: APIs connect disparate software applications as they enhance the overall application or product performance.
• Ease development cycle: APIs help developers shorten the software development cycle. API automation holds the key as computers are used to manage work rather than a manual task force. APIs allow companies to update their workflows at once.
• Efficiency: With API access, content once generated can be easily shared and redistributed across various channels.
• Personalization: APIs enable customizations. Any user or company can take advantage of this by personalizing the content or services as per their need.

The Difference between an SDK and API

Let’s understand the difference between the two constituents with examples.

Facebook provides a suite of solutions that offer tools for professional developers as well as active users. It has both an API and an SDK. Both these tools are entitled to perform different functionalities and are use-case specific. We will begin with the APIs.

Facebook APIs

In partnership with third-party developers, Facebook APIs connect to Facebook and access required data about a user. This is used to personalize application functions.

For example, a movie booking app uses the Facebook API to let you log in to the app using your Facebook ID. Your name and profile details are shared with the movie booking app to ensure the authenticity of the user and to let you avoid remembering a separate login and password. It also allows the movie-booking app to show you relevant ads as you browse your Facebook feed.

One of the USPs of the API includes how it couples with a Graph API explorer. The Graph API service builds relational data between users, accounts, updates, groups, and more.

GET graph.facebook.com/me?fields=posts.limit(5){message}

Here we observe a sample API issuance for better understanding. The above call will retrieve up to five posts you have published and the text for each individual post.

Let’s take another example.

GET graph.facebook.com/me?fields=posts.limit(5){message,privacy{value}}

The above API query returns the text and privacy settings of each post that you have published.

Both APIs run under Graph API, thereby aiding in analytics generation (i.e., relational data).

Although the above example is a simple use case, consider another scenario where a restaurant owner wants to list users who attended a party at their restaurant. The owner could use a Facebook API call and generate a list of users present during the function by accessing the photos clicked at the party and the tagged Facebook users.

Additionally, the restaurant authorities could also have a list of users’ social accounts and use them for future promotions. Without APIs, leveraging such functionalities can be cumbersome to develop. Next, we will look at Facebook SDKs.

Facebook SDKs

SDKs provided by Facebook are specifically designed for “application creation”. For example, there are many games you can play within the Facebook app. These are designed to run within Facebook, and you need an SDK to create these apps.

Let’s look at the Facebook SDK for iOS. It allows the development of Facebook applications for iOS in specific.

Consider the following code snippet disclosing Facebook SDK for iOS:

/**
 * For more details, please take a look at:
 * developers.facebook.com/docs/reference/ios/current/class/FBSDKAppEvents
 */
- (void)applicationDidBecomeActive:(UIApplication *)application {    
    [FBSDKAppEvents activateApp];    
}

The above example is used for logging events related to application activations.

The structure of the call varies in both cases. An API performs an action that is pre-defined via existing sources and functions. On the contrary, the SDK first defines the function and then calls the source and the function.

Choosing Between an SDK and API

APIs essentially outlines how disparate platforms can work together synchronously. They assist in application integration via protocols and specifications. Thus, they are one of the critical components of an SDK. APIs, however, cannot be used to create apps from scratch.

SDKs facilitate building a new application or software that is specific to one programming language or platform. An SDK generally has at least one API to communicate externally.

If you are building an app to run on a specific platform, such as iOS, use the SDK for that platform. To communicate with other web applications like Facebook, use the API of that app.

Conclusion 👨‍🏫

In summary, the difference between an SDK and API is highlighted in the following postulates:

• SDKs often contain APIs, but no API includes SDKs.
• Like a foundation of a house that allows the house to stand tall, SDKs enable the creation of applications.
• APIs decide the functioning and communication of applications within the SDKs, similar to the phone lines that allow contact with the outside world.