What is an API? Application programming interfaces explained

Server applications aren’t allowed to store any data related to a client request. The difference between an API and a web application is that API allows two-way communication and web applications are just a way for users to interact through a web browser. Paw is a full-featured HTTP client that lets you test and describe the APIs you build or consume.

Consider enrolling in a beginner-friendly, self-paced online course like Meta’s Back End Developer Professional Certificate. You’ll acquire and apply your skills to build a portfolio not only using APIs, but also programming systems like Python syntax, Linux commands, Git, SQL, Cloud Hosting, Version Control, JSON, and XML. Be it web APIs that connect web applications to other platforms or APIs used by IoT devices to collect and process data, the use of APIs has expanded like never before. They identify the application and ensure it has the access rights required to make the particular API call. API keys are not as secure as tokens but they allow API monitoring in order to gather data on usage. You may have noticed a long string of characters and numbers in your browser URL when you visit different websites.

Restrictions of Using APIs

Each system is obliged to make internal changes so that the API is not impacted. This way, any future code changes by one party do not impact the other party. The client completes a function (or procedure) on the server, and the server sends the output back to the client. Every time you use a rideshare app, send a mobile payment, or change the thermostat temperature from your phone, you’re using an API.

Similarly, a server application shouldn’t modify the client application other than passing it to the requested data via HTTP. An API acts as an interface that allows proper communication between two programs whereas a web application is a network-based resource responsible for completing a single task. Also, it’s important to know that “All web services are APIs, but not all APIs are web”. A microservices architecture essentially uses remote APIs for activities that were traditionally done by local API. A microservices architecture decomposes an application into components that are remotely available.


Donations to freeCodeCamp go toward our education initiatives, and help pay for servers, services, and staff. A content writer and editor with a history of self-learning multiple skills. An API is an interface for two computers to communicate in order to carry out tasks on the internet.

api explanation

When these types of APIs are put to action, they help facilitate client-server communications with ease and smoothness. Because REST-based APIs are simple, they can be the perfect APIs for beginners. REST defines a set of functions like GET, PUT, DELETE, etc. that clients can use to access server data.

APIs and good software design

APIs are a gateway that present an organization’s systems and data to internal and external users. Using the same rules and formats streamlines code and makes it more transparent. Standardization also facilitates collaboration among developers as they build software components with the intent to integrate with APIs. This, in turn, facilitates feature development and reduces time to market.

  • Consider enrolling in a beginner-friendly, self-paced online course like Meta’s Back End Developer Professional Certificate.
  • SOAP is a protocol while REST is a set of constraints that constitute an architectural style.
  • APIs can be categorized by use case, including data APIs, operating system APIs, remote APIs and web APIs.
  • APIs are a gateway that present an organization’s systems and data to internal and external users.
  • In effect, these API protocols facilitate standardized information exchange.
  • TAPI (Telephony Application Programming Interface), and .NET are common examples of Local APIs.

APIs are mechanisms that enable two software components to communicate with each other using a set of definitions and protocols. For example, the weather bureau’s software system contains daily weather data. The weather app on your phone “talks” to this system via APIs and shows you daily weather updates on your phone. An application programming interface can be synchronous or asynchronous. Connect applications, data, business processes and services, whether they are hosted on-premises, in a private cloud or within a public cloud environment. Many companies choose to offer APIs for free, at least initially, so that they can build an audience of developers around their brand and forge relationships with potential partners.

What are the different types of APIs?

All API requests for the same resource should look the same, no matter where the request comes from. The REST API should ensure that the same piece of data, such as the name or email address of a user, belongs to only one uniform resource identifier (URI). Resources shouldn’t be too large but should contain every piece of information that the client might need. It is implemented to extend the functionality of a browser, simplify complex functions, and provide easy syntax to complex code. Its main feature is that REST API is stateless, i.e., the servers do not save clients’ data between requests. This contains rules guiding requests and responses sent from web applications using XML between systems through Hypertext Transfer Protocol (HTTP).

api explanation

APIs are an integral part of the growth in software as a service (SaaS) products. This integration drastically reduces time spent switching between applications for sales and marketing tasks. It also helps reduce or prevent data silos that might exist between departments that use IT blog different applications. Travel booking sites aggregate thousands of flights, showcasing the cheapest options for every date and destination. APIs enable this service by providing application users access to the latest information about availability from hotels and airlines.

The server can send callback messages to connected clients, making it more efficient than REST API. These APIs are well documented for both consumption and versioning in the process. Additionally, today, APIs are treated more like products than code.

api explanation

This means that testing your API endpoints might be a tricky process after developing them. Fortunately, there are amazing tools out there that I will share to help you test your APIs efficiently. Programming is made simpler by using APIs to abstract away certain implementations, and expose actions or endpoints to developers who need to consume the endpoints when building applications. Programming paradigms like object oriented programming and functional programming take different approaches to facilitating the development of good APIs. Object-oriented programming encourages strong encapsulation, whereas functional programming exposes functionality to facilitate code flow.

The browser API

Once the prototype is tested, developers can customize it to internal specifications. The term “API” has been generically used to describe connectivity interfaces to an application. However, over the years, the modern API has taken on some unique characteristics that have truly transformed the technology space.

api explanation

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