Application Programming Interface (API): Definition, Types and Examples

Introduction:

Do you even remember when was the last time you manually typed your email ID to log in or sign up for a web or mobile app? No, right. We all sign up using either Google or social channels. This is an ideal example of how APIs make our lives so simple. 

APIs are such a crucial part of software development. Each day, we all use APIs so many times unknowingly. No matter how long you’ve been using software or adore cutting-edge technology, you need to know what an API is and why it matters. The blog will explain APIs and their significance in today’s technological world.

Also read, The Ultimate Guide to API Development: Types, Examples, and Best Practices

What is an Application Programming Interface?

Developers often create what is known as an “Application Programming Interface" (API) that facilitates communication between software. It enables a single software program to take advantage of functionalities available in another software. APIs are present in almost every industry, where they facilitate data exchange.

APIs are used by large software companies like Meta, Amazon, and SalesForce so that other businesses may access their services without having to overhaul their IT systems fully. Experts have coined this phenomenon the “API economy,” which has improved corporate efficiency and created new systems by building upon existing ones. For instance, in financial trading, APIs link automated trading systems to a trader’s platform, providing the trader access to real-time data and facilitating the execution of deals electronically.

How do APIs work?

One of the most prevalent uses of APIs is in the realm of online payment processing. When purchasing an online store, customers are often given the option to “Pay with Paypal” or another external payment gateway. For this to work, we rely on a connection being made by APIs.

• An application programming interface (API) makes a request when a customer hits the “buy now” button. This request has a verb, headers, and occasionally a body and is sent from an application to a web server using the API’s Uniform Resource Identifier (URI). 
• An external software or web server, in this instance, the third-party payment system, is contacted by the API once it has received a valid request from the product page. 
• Once the API requests data from the server, the server responds with the concerned data.  
• In this case, the product website receives the data from the API and uses it in its operations. 
• Regardless of whether web service is utilized, all requests and answers are handled by an application programming interface (API). Still, the specifics of the data transmission may vary. APIs communicate data inside the computer or program; to the user, it is a smooth connection since they are not visible on the user interface.

Why use an API?

APIs are like the unseen heroes of the Internet. For changing and boosting your business, they are the key. The major reasons for using APIs are as follows: 

• Ensure better customer experience: 

When it comes to your consumers, APIs can do wonders. They simplify how they use your services, which makes it easier and more convenient for them. Consider how third-party apps work with your favorite online stores, improving the shopping experience. That fascination is created via APIs.

• Data sharing and synergy creation:

APIs facilitate the distribution of data. When you release information to the public, it might be used by other developers for their purposes. Working together may build synergy that can benefit your company and encourage new ideas. It’s similar to a knowledge-sharing ecosystem that couldn’t exist without APIs. 

• Managing Information Efficiently:

In the corporate world, data is invaluable, but its collection and management may take time and effort. APIs make this much easier to do. They make it simple to gather data, which is particularly useful when searching for targeted details. APIs can handle and analyze massive volumes of complicated data, simplifying decision-making.

• Helps companies to grow: 

Using APIs is the way to grow your business. They provide access to other resources like software and web pages. For instance, if you own an online store, you might let programmers use your API to build extensions like payment processors and dropshipping tools. 

• Facilitating Better Teamwork and Communication:

APIs play a key role in facilitating digital interaction. They improve communication and collaboration across your company’s various teams and divisions. These factors elevate production quality, streamline operations, and drive a company to greater success.

Also read, The Ultimate Guide to AI Chatbots for eCommerce

How to Create APIs?

APIs are the backbone of all the programs and websites you use daily. They’re the glue that holds together our disparate software platforms. But the question is, “How do you make one?” Let’s simplify it by breaking it into these parts:

Identify your requirements first

The first step is to define the goals of your API. The following items constitute your “requirements.” There will be two categories of requirements to consider: functional and non-functional.

• Functional Requirements: These are the responsibilities of your API. How much of its functionality and data should be made available to other programs? 
• Non-functional Requirements: This is the small print. Think about safety, speed, and performance. How quickly should your API respond? To what extent will data be protected?

To determine the goal of your API, you may ask questions like:

• Who is going to use your API? Customers inside or outside your business, or both?
• To what extent can you accommodate such users?
• What safety precautions should you take?
• What kind of speed and responsiveness are you anticipating?

Plan Your API Design

Having determined the purpose of your API, you can move on to its actual implementation. This stage is analogous to creating a blueprint. When using your API, what will the interface look like? Consider the rules and instructions you wish to follow. Do you need to follow a certain set of rules when you design? You can create the interface before building the parts that connect to the software.

Develop your API

It is time to roll up your sleeves and begin developing your API. Consider the following steps: 

• Name your API: You must provide a name and description for your API for better user clarity. 
• Identify Functions: What will your API be used for exactly? Lay down the specifics of the data transmission and reception.
• Data Models: Make clear how the data in requests and replies will be organized.
• Non-functional features: Set up safeguards, caches, rate limits, and other unique features.

The API’s interface will be specified in a specialized language (Open API Specification (OAS), Swagger, RAML, or WSDL for RESTful or SOAP APIs, respectively). These are the rules and requirements that your API must adhere to.

QA and Test 

Your API has to be thoroughly tested before it can be used. This is where you’ll verify the system’s robustness under varying inputs. You will ensure its safety and that it satisfies your other non-functional needs. Consider the following steps while testing: 

• Testing Environment: Your API should be tested in an environment where it can communicate with a replica of the production system or generate dummy replies without live information.
• API Testing: Get some tools and try out your API. Integrate a full-featured API testing solution with your API management platform. This ensures that your API is working properly.

Publish / Deploy 

As soon as your API has passed testing, it would help if you made it available to the public. It’s the same as welcoming customers into a shop. Consider the following things in this step of creating APIs: 

• Production deployment: If you’re ready to put your API into production, you must deploy it to a server or platform. It is hosted on an API gateway to guarantee its swiftness, safety, and dependability.
• API Developer portal: Make a site for API developers to showcase your API and encourage others to utilize it. Your API’s purpose, implementation, and protections should all be spelled out in this central hub’s accompanying documentation. Various subscription tiers need to be available.
• Interactive Testing Tool: An interactive testing tool should be available to ensure that developers can test your API without affecting production systems or data. 

Keep Monitoring

It would help if you kept an eye on how API is used and how it functions.

• Monitor operational metrics, including availability, response time, and request volume.
• See how often your API is used and whether developers are interested.
• Use appropriate business metrics to check whether your API is providing the anticipated benefits to your company.

How to Use an API?

It may seem complicated to use an API, but it’s pretty easy. Please consider the following to learn how to use an API:

• Step1: Select an API: 

The first step is to choose an appropriate API. Depending on the needs of your project, you may discover free or premium APIs. 

• Step 2: Obtain an API Key: 

To have access to API resources, you will need an API key. It’s a requirement for the API to verify your identity and maintain track of your activity. Some APIs do not charge for access keys, and some do. Get your private API key when you register for our API service.

• Step 3: Have a look at the API Documentation: 

The API documentation serves as the guidebook. Instructions for obtaining an API key, submitting queries, and retrieving data are detailed. Having clear instructions for using the API is essential.

• Step 4: Make a Request:

It’s time to make your first API call. There’s no requirement for you to know how to code. Requests may be organized and sent with the aid of an HTTP client. What kinds of requests are acceptable will be outlined in the docs.

• Step 5: Connect your App: 

Here’s your chance to show off your skills as a programmer. You’ll be establishing a link between your app and the API. Various programming languages will be required, including Python, Java, JavaScript, PHP, and others. The API will communicate with your app, and you will implement the necessary code.

Types of APIs

Most APIs used nowadays are web APIs that provide access to an app’s data and features via HTTP. We may classify web APIs into four broad categories:

• Open APIs: Open APIs are programming interfaces that are freely available to the public and may be accessed via the World Wide Web. These APIs are available to the public and have well-defined API endpoints and request/response formats. 
• Partner APIs: Strategic business partners can talk to each other through partner APIs. A public API developer site typically provides developers with self-service access to these APIs. However, before users can use partner APIs, they must complete an onboarding procedure and get login credentials. 
• Internal APIs: The internal APIs are not exposed to the public. These internal APIs are not accessible to the general public and are designed to facilitate coordination and collaboration across the company’s many development groups. 
• Composite APIs: Composite APIs merge many different APIs into one. They make it possible for developers to make a single call to several destinations. Composite APIs come in handy when a single operation requires data from many services in a microservices architecture.

How do APIs enable digital transformation?

APIs have been the driving force behind the digital transformation that has completely transformed enterprises in recent years. Some of the major reasons for such an efficient digital transformation are: 

• Without much time or money, they are crucial in facilitating efficiency and driving innovation. 
• APIs provide for the safe and effective transfer of information, streamlining complicated processes and lightening administrative loads. This boosts productivity and creates space for novel income streams and organizational structures. Opportunities for innovation and responsiveness to changing market needs are made possible by APIs’ open access to data, resources, and services. 
• On top of that, APIs do away with the necessity for manual data interchange across various systems, allowing for the timely and accurate delivery of critical information. Automation helps businesses make smarter decisions and provide superior customer service by increasing data accuracy and reducing processing times. 

Advantages of APIs

APIs provide a plethora of advantages that streamline and accelerate our digital lives: 

• Enhanced Collaboration: 

In the corporate world, we rely on a wide variety of programs and platforms, not all of which are compatible with one another. Because of APIs, communication between these software programs is no longer an issue. As a result, you’ll be able to streamline processes and boost productivity via teamwork. Data would be isolated in silos without APIs, slowing down and complicating operations.

• Speeding up innovation:

When it comes to new opportunities, APIs are like links. They allow companies to form alliances, expand their product lines, and enter new markets. Consider Stripe, a company that has grown from its humble beginnings as a seven-line API to become a major player in the financial industry. APIs encourage creativity and promote economic expansion.

• Data Monetization: 

To foster partnerships with developers, some companies provide APIs at no cost. However, companies may monetize their API if it provides access to valuable data. The result is what we refer to as the “API economy.” 

• System Security: 

By isolating the requesting app from the service it’s communicating with, APIs increase the system’s overall safety. Authentication is necessary, and they use many layers of protection during data transfers and access control. This safeguards your information from potential cyberattacks.

• Privacy and Safety for Individual Users:

APIs provide an additional layer of protection for the rest of us, everyday users. The API is a filter that determines which websites and apps have permission to access your information. You have the option of granting or denying access in this situation. It’s the equivalent of saying, “Go ahead and look at my personal information” before someone else does.

Disadvantages of APIs

• Security Issues: 

Protecting API systems from security breaches like SQL injection attacks and cross-site scripting (XSS) attacks is very important.

• Complexity: 

The implementation and upkeep of APIs may be time-consuming and difficult because of their complexity.

• Problems with Compatibility: 

Inconsistencies in API compatibility across software versions or between platforms might cause unexpected behavior or even system failure.

• Reliance on Third-party Programmers:

Third-party programmers use APIs to build programs that work with the main software. Because of this, the software’s owner may be forced to rely on third-party services outside their control.

• Management and administration: 

They must be properly governed and managed to guarantee that APIs are used appropriately and consistently across multiple applications and systems.

Examples of APIs

Examples of frequently seen API use are as follows:

• Universal logins: 

The ability to sign into a website using one’s existing account information from a social media platform like Facebook, Twitter, or Google is a common example of an API. By using an API from one of the most widely used services, any website may quickly and easily authenticate its users without requiring each user to create a new profile.

• The IoT, or Internet of Things: 

The API on these “smart devices” allows for extra features like internet-connected touchscreens and data collecting. A smart fridge, for instance, may sync with recipe apps or capture and text message notes to nearby mobile devices. The fridge’s built-in cameras may be linked to third-party apps so owners can check on their perishable goods anywhere.

• Twitter: 

Each Tweet has its own identifying characteristics, such as its creator, identifier, message, posting time, and geographical data. Twitter’s API provides access to the most essential data about public Tweets and responses and enables embedding Tweets in third-party websites.

• Travel Booking Comparisons: 

Flights may be expensive, but luckily, booking companies compile dozens of flights and provide the best deals for each day and location. This is made feasible via API, which provides app users access to real-time hotel and airline availability data via any web browser or the booking service’s native app. APIs drastically reduce the time and effort needed to look for flight or hotel availability by allowing for the autonomous interchange of data and queries.

• Mapping Apps: 

These applications leverage additional APIs and capabilities to provide users with information like directions, speed restrictions, sites of interest, traffic alerts, and more, in addition to the basic APIs that show static or interactive maps. Users interact with an API to plan routes or monitor the whereabouts of a moving object (such as a delivery van).

• Software as a Service: 

The proliferation of “SaaS” (software as a service) offerings is inextricably linked to APIs. APIs are often included in platforms like CRMs (customer relationship management tools), allowing businesses to link with other programs they currently use. As a result, you’ll spend far less time doing various sales and marketing chores in different programs. It also helps eliminate the possibility of data silos developing across departments using different software.

Differences Between APIs and Web Services

Core Purpose: 

• Web Services: These rules and methods allow different systems or apps to share info. They facilitate the transfer of information. 
• APIs: APIs function as a digital handshake between programs, allowing them to exchange data and work together. They make it possible to have conversations without actively involving the audience.

Methods of Exchange

• Web Services: Different restrictions apply to the various forms of communication that Web services enable, such as REST, SOAP, and XML-RPC.
• APIs: APIs are flexible and may be used for various communication.

1. Supported Protocols: 

• Web Services: Use the Hypertext Transfer Protocol (HTTP) primarily.
• APIs: Maintain compatibility with the original HTTP and the encrypted HTTPS protocol.

Data Formats

• Web Services: Use XML as the data type most of the time.
• APIs: APIs accommodate a wider variety of data types, including XML and JSON, facilitating fast and versatile data interchange.

While it’s true that all web services are APIs, this is only sometimes the case in reverse. Some APIs aren’t web services. The flexibility of APIs in contemporary software development stems from their general use and their adaptability to different interface paradigms. In contrast, web services are a form of API developed for specific protocols and standards in web-based communication.

Also read, Generative AI: Use Cases, Benefits, and Models in 2025

Some of the Key API Protocols

APIs adhere to a set of guidelines; these are known as “API protocols.” Let’s look at some of the most common API protocols that facilitate the exchange of information between applications.

SOAP (Simple Objects Access Protocol):

SOAP functions in a similar way to an XML-based API. Since it was created in 1998, it is one of the oldest API protocols. It employs XML files sent over HTTP/HTTPS (the encrypted form of HTTP) to communicate across online services. 

The four basic components of a SOAP message are the “envelope,” “header,” “body,” and “fault.” The “envelope” carries the whole message, while the “header” provides optional further information. SOAP is very adaptable and can communicate via a variety of transport protocols. However, the XML format it uses may be stiff at times.

REST (Representational State Transfer):

REST is compatible with several types of data files, including the widely used JSON format, HTML, plain text, and even audio and video files. It uses just the HTTP/HTTPS protocol for data transfer, which is far less complex and resource-intensive. RESTful APIs are application programming interfaces that adhere to the REST architectural style.

Unlike other client-server approaches, REST is stateless; it does not save user information between requests. Separate requests are being made here. It gives each task its URL, which tells the server precisely what to perform when it receives a request. The caching feature, which REST supports, allows quicker replies by storing data locally in the browser.

(JSON-RPC) JavaScript Object Notation- Remote Procedure Call:

JSON-RPC is a protocol for exchanging API data in JSON format. It could be more flexible, but it works well for some jobs. It is stateless and lightweight. With JSON-RPC, online services more easily communicate by exchanging request and response objects.

gRPC (Google Remote Procedure Call)

Google’s gRPC is an impressive open-source Remote Procedure Call (RPC) framework. It can adapt to different settings with ease. The unique feature of gRPC is that it allows programmers to write their custom functions to facilitate communication in any situation.

It uses protocol buffers to arrange data in a manner that is independent of the underlying platform and uses HTTP as its transport layer. The service and the corresponding data structures are first defined in a protocol buffer. In turn, these definitions are used by a compiler to produce executable code.

GraphQL

Facebook developed GraphQL which represents a new approach. It’s not quite an API protocol but more a query language. Instead of downloading a pre-formatted data set, a query is sent to the server detailing the information sought and the format in which it should be returned. The server sent back the data you requested.

This method reduces data storage needs and processing burdens by delivering just the information sought. A difficulty with caching arises when you need to retrieve supplementary data that wasn’t included in your first request.

XML-RPC (Extensible Markup Language Remote Procedure Call):

XML-RPC is quite similar to JSON-RPC, except it uses XML rather than JSON to carry out data exchanges. It uses HTTP/HTTPS for communication and adheres to a predetermined set of vocabularies for constructing requests and answers. The client requests a certain function call from the server and specifies its arguments.

Despite its ease of use, XML-RPC has limits, particularly when dealing with sophisticated data structures or information outside its established vocabulary.

Apache Thrift

Apache Thrift, created by Facebook, is another method for developing APIs. Code generation takes precedence over rule setting. APIs may be generated with Apache Thrift’s help thanks to the engine and stack it employs. Thrift files are used to initialize the client and server.

With these specifications, the code generator may produce code in your chosen programming language. Apache Thrift’s primary goals are scalability and facilitating communication across services written in various languages.

REST vs. GraphQL vs. SOAP APIs

When it comes to APIs, not all of them are the same. Which one is best for you depends on your requirements and situation. Let’s compare REST, GraphQL, and SOAP to see which is best for you.

Rest API

Advantages:

• It’s simple to set up, making it a fantastic option for beginners.
• It’s HTTP-based so regular web browsers can access it.
• Lightweight communication formats make it scalable, efficient, and quick.

Disadvantages:

• Sometimes, there need to be more built-in safety features.
• Notifying the client of state changes but does not control it.

SOAP API:

Advantages:

• A reliable option for creating and managing APIs in large-scale business settings.
• Provides pre-defined and standardized scalability.
• Built-in safeguards against malfunctioning.

Disadvantages:

• Due to its rigidity, it is slower to change and adapt.
• Developers with less experience with SOAP will need more time for training.
• Utilizes XML for all communication, which might slow things down.

GraphQL API: 

Advantages:

• Effectiveness in retrieving just the information required without wasting time on unnecessary or duplicate data requests.
• Saves time and data transfer by retrieving numerous resources in a single request.
• This is a great solution for exact querying and complicated systems.

Disadvantages:

• Does not have cache support by default.
• Complex searches often have performance issues.
• I Need time to fully understand how complicated it is.

REST is wonderful for ease of use and speed, SOAP for sturdiness in business applications, and GraphQL for pinpoint data retrieval in complicated systems. Your project’s needs, your team’s skills, and your ultimate objectives should all factor into your decision.

Also read, How to Hire The Best Mobile App Development Company

Conclusion

APIs are essential to the smooth flow of information and the development of new technologies in today’s related digital world. They streamline the development process, encourage teamwork, and boost productivity in enterprises. Organizations may improve efficiency and customer satisfaction via API creation and use due to a well-defined methodology.

Glasier Inc. is a leading software development company. We build and integrate custom APIs to help businesses establish better communication between software. If you want to build a custom API, reach out to us at 079 4900 0109 for a free consultation or quote.