You may not be familiar with the concept of API unless you are in the software business, but if you are on the internet, you sort of need to be! In this golden age of the internet, if you have any presence on the web, whether it is on social media or using a simple weather app, rest assured that you are enjoying your experience due to the API.

In this post, we’ll be covering what an API is, the importance of an API, where it is used, who uses it, how it works, and types of API.

What is an API?

Simply put, API (Application Programming Interface) helps different software communicate with each other. API accesses the data and features of applications, services, or operating systems which ultimately allows different and unrelated applications to “talk” to each other.

The most crucial aspect of an API is that instead of using big piles of data to extract a little piece of information, it pulls necessary data without any additional investigation or manipulation which makes it more effective and on point when it comes to delivering the best results.

Why is an API important?

The API has come a long way since the term was first coined in the late 1960s. Current API codes are highly business-relevant. Organizations now use an API to access multiple systems and break down applications into smaller, more manageable, and scalable components. The simplicity of the current API manages to demonstrate its worth to the business while speaking its language and keeping it simple when it comes to serving its rather complex service implementation.

With the assistance of an API, businesses can operate faster and more innovatively in terms of discovering new digital capabilities. Needless to say, all this creates more user-friendly experiences for the consumers.

Who uses an API and where?

It would not be unreasonable to say that most industries around the globe benefit from an API effectively. From big tech companies to government agencies and the world of e-commerce, an API is used mainly due to its convenience, security, and connectivity.

Believe it or not, without an API, our online experiences would have been far more complicated than they are now. For instance, an android app that uses touch ID would have had to develop a whole new custom software if it was not for the API, or the weather app on your phone would have been unable to pull data so easily from different sources and show you the weather at your current location in the most accurate way which would have ultimately served as a less user-friendly experience.

Let’s make this more definitive by giving a detailed real-life example. Say, you are planning your summer vacation. You start looking for the most cost-effective way to travel to your summer location and decide that using the bus is the best option. You also would like to add other information such as the date, specific bus stations you would like to depart from and arrive at, seat preferences, etc. Instead of checking the specific bus companies’ websites one by one, you decide to click on a wholesaler website. This website lists the tickets from least expensive to most along with other information that you picked from the drop-down menu. The website is collecting all the necessary information from multiple bus companies’ websites, and that’s where the API becomes relevant. An API helps this wholesaler to pick the most precise information from multiple companies’ databases and deliver what you are looking for.

It is important to know that during this transaction, your personal data is never fully exposed to the server and vice versa, which means the API also provides an extra layer of security. Only the most relevant and necessary data is shared while keeping your personal information secured at all times.

How does it work?

While using a simple social media app, one of the most important selling points would be to navigate a not-so-complicated user interface. While keeping it simple, the user - in our case, a human being - simply interacts with the app through this interface. The same goes for an API but in this case, it is intended to be used by a computer or another application. It basically serves as a middleman between the server and the program.

That being said, an API keeps it abstract in a way that the server does not need to know how the application works. The only key point would be to understand how the API retracts the data it needs to display. The same goes for the end consumer. The consumer does not need to know how the API works as long as they can navigate the interface comfortably, in line with their needs.

Performing these tasks requires a very high level of security. So how does an API keep all the sensitive data to itself during the transaction? In order to understand that, we need a quick introduction to the term “API keys”. API keys serve as an ID card for the user who is making an API request which serves as an authenticator. This identifier serves a very specific purpose which enables it to merely give the necessary access permissions and monitor how these permissions are being used by the user. Once the key suspects an invalid and suspicious act, it tracks down the user and takes necessary measures. An API directly checks with its client’s database weather to grant the requested permissions or not. API users also benefit from these keys by tracking down the number of clients asking for permissions, the content of the permissions requested by specific clients, the volume of the requests and keeping a record of these interactions overall.

By doing all this, API keys protect their users from potential harm that may be caused by hackers. The keys can minimize bot traffic and ban specific users from requesting and accessing permissions.

Types of APIs

It is important to mention that while most commonly used on the web, not all APIs are specific to web applications. There are other types of APIs that are used by machines and systems that need to interact with one another. API types come in a variety of options, serving a specific purpose to developers for their suite of needs. One way to categorize APIs is by listing them in terms of their targeted user or audience. There are basically four types of API: Public API, Private API, Partner API, and Composite API.

  1. Public API

Also known as an open API, a public API refers to APIs that are available for general use. These types of APIs are relatively less restrictive than others, which enables the general public to benefit from the system or, in most cases, the application collectively. A couple of the most common examples of this type of API would be Google Maps and YouTube. Developers from outside can build applications that retrieve information from Google Maps and YouTube to benefit from their APIs. While this is the case, it is important to note that not all public APIs are entirely open for general use but also require additional approval for other applications to extract specific information.

An open API does not necessarily mean leaving behind all security measures. However, it is understandably less isolated than other APIs. This may become an advantage in terms of positive user experience due to the fact that its service is commonly free of charge and does not always require a subscription. Due to these properties, it can also be said that these types of APIs reinforce innovation while maintaining market dominance.

  1. Private API

A private or closed API commonly refers to internal use. The main difference between a public and private API is that users who are granted access to the domain are able to use the latter API. Private APIs serve the purpose of building transparency while keeping productivity at a maximum capacity. Developers or users from outside are unable to access the private API, which makes internal communication secure. Implementing a good private API takes a lot of measures. The best way to treat these types of APIs would be to imagine that they are open to dangerous exposure at some point and build them accordingly. A few examples of private APIs would be Customer Relationship Management programs (CRM), Enterprise Resource Planning programs (ERP), and financial programs.

  1. Partner API

Partner APIs are similar to private APIs in that only specific collaborators can access them. In this case, different strategic partners can access these APIs via specific authentication and authorization systems. Due to them being open to multiple partners, these types of APIs require additional security protocols. Having central administration, maintenance, version management, and tracking of API consumption will increase the adoption rate, regulate usage, as well as secure and protect the IT infrastructure.

It may help to start with a private API that is 100% internal. This can help establish the right data architecture without the pressure of meeting the needs of any outside partners. Then, with the right architecture and processes in place, suitable partners can be detected accordingly.

With this type of API, developers have a simple, streamlined way to build new business relationships between technologies, creating huge opportunities for mutually beneficial partnerships in a variety of industries. While it can be difficult and time-consuming at times, partner APIs provide more exposure, brand recognition, higher demand, and a revenue stream for included parties.

  1. Composite API

Recently added to the list of API types, composite or batch APIs basically combine several API requests into one API call. This enables keeping API calls to a minimum while keeping the application more effective and less time-consuming. If you need data from different applications, you would use a composite API. Instead of making multiple separate API calls in succession, you can make only one using a composite API.

One example of a composite API would be logging into an e-commerce website, creating a user ID and password, creating a cart, adding items to the cart, and removing the items from that cart, eventually changing the order status. All these actions are bundled together in a composite API and sent to the server while receiving only one response. This way, composite APIs make life easier for both customers and developers.

In order to implement these aforementioned types of APIs, we need to follow certain guidelines and protocols. Without these defined rules, API calls would be unable to specify the data types and certain commands. Therefore, another way to categorize APIs is by their architecture and protocols. Here are the categories being used by API developers:


The REST (Representational State Transfer) design is an approach to communications that favors a generally straightforward interface between components (clients and servers). It emphasizes a restricted number of well-defined operations, each with a standard set of contention formats.

In order for an API to be RESTful, it needs to follow certain parameters:

  • A stateless user-server architecture, which means each request contains all of the information necessary to accomplish its task. (Stateful services keep track of sessions or transactions and react differently to the same inputs based on that history. Stateless services rely on clients to maintain sessions and center around operations that manipulate resources, rather than the state.)

  • A user and a server should communicate with one another via HTTP (HyperText Transfer Protocol) using URIs (Unique Resource Identifiers), CRUD (Create, Read, Update, Delete), and JSON (JavaScript Object Notation) conventions.

  • The user and server should be independent of each other. Any updates or changes on the server should not affect the user in any case.

  • The user should cache the responses as this improves the user experience by making them faster and more efficient.

  • The API should support a layered architecture, with each layer contributing to a clear hierarchy. Each layer should be loosely coupled and allow for encapsulation.

Most modern web applications, such as Netflix, Amazon, Uber, etc., are benefiting from this type of architecture as it allows their customers to enjoy interacting with the websites and applications more effectively.

Web APIs that comply with REST architectural constraints are called RESTful APIs, as we have already mentioned. These APIs use HTTP requests (AKA methods or verbs) to work with resources: GET, PUT, HEAD, POST, PATCH, CONNECT, TRACE, OPTIONS, and DELETE.

RESTful systems support communication in different formats, such as plain text, HTML (Hypertext Markup Language), YAML (commonly known as Yet Another Markup Language), XML (Extensible Markup Language), and JSON, while SOAP only allows XML, which we will mention in the upcoming category. The ability to support multiple formats for storing and exchanging data is one of the reasons REST is a prevailing choice for building public APIs.


SOAP (Simple Object Access Protocol) design is a method for communication between different systems through an XML document. These documents are mostly used in web services and assist the involved systems in communicating with each other, passing information back and forth over a network connection. This type of API is more strict when it comes to defining the means of communication. It thoroughly defines how one application will interact with an external system.

SOAP is better suited for businesses that require a more profound and customized approach to data sharing. It provides total control over how you trade information with other parties, which means there are fewer security flaws than with other means of communication. It is commonly used for payment gateways, identity verification, and telecommunication services.


Being the oldest and least complicated type of API, RPC (Remote Procedure Call) basically allows two computers that need data requests from each other to communicate. That being said, it is harder to maintain and update RPC APIs compared to other architectural API types. For example, an RPC can be used to make client or server calls from your chosen interface. This can happen on your computer or through a web connection between servers. Either way, RPC allows you to access and utilize code stored remotely.

When used for CRUD (a software application in which users must be able to create data, have access to the data in the UI by reading the data, update or edit the data, and delete the data), RPC is just a case of sending up and down data fields. One downside is that the user is entirely in charge of pretty much everything. They must know which methods (endpoints) to hit at what time to construct their workflow out of otherwise naive and non-descriptive endpoints.


Initially created by Facebook during the 2010s, GraphQL is an inquiry language for APIs. It allows the user to specify the precise information they need and streamlines information accumulation from different sources, so the developer can use one API call to ask for all the required information. In simple words, it gives the user the power to request exactly what is necessary with a simple and complete description.

Compared to other APIs, which have a single-point-of-failure model, meaning one outage can take down an entire business or application, that is not the case for GraphQL. With a highly scalable GraphQL back end, one can get a rapid response time even with thousands of concurrent users.

While the REST API requires extracting data from multiple sources through multiple requests, GraphQL does all this in one combined request. Time effectiveness being way too valuable these days, most mobile applications prefer this approach since it allows them to be quick on even slow network connections.

In the complex world of APIs, one can see that this piece of code not only helps make the online world a better place but also provides many different types of businesses an easier approach to their customer experience and overall business management. With assistance from APIs, businesses and customers have a better chance of understanding the importance of technological connectivity, which mainly explains why 83% of participants find API integration “critical” to their businesses and IT infrastructures, according to the Fourth State of API Integration Report of 2020.

It is important to mention that the types of APIs mentioned in the previous sections are not an exhaustive list, and there are other types of APIs available as well. For example, there are event-driven APIs, which trigger a response when an event occurs, and streaming APIs, which provide a continuous stream of data rather than waiting for a request.

Regardless of the type of API, it is important for developers to follow certain guidelines and protocols to ensure the API is secure and efficient. For example, APIs should use authentication and access control to prevent unauthorized access, and they should be designed with scalability in mind to handle increasing traffic.

Overall, APIs have become a crucial component of modern software development, allowing developers to build powerful applications that can integrate with a wide range of services and systems. As technology continues to advance, it is likely that APIs will become even more important, and developers will need to continue to learn and adapt to stay ahead of the curve.

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