What is an API?

Have you ever wondered how different software programs talk to each other? Because they do. They might not engage in sophisticated debates or co-host current-affairs podcasts or exchange tweets — at least not yet. But every day, software components chat with one another in order to make the tech world go round.

It’s true: communication between digital technologies is a fundamental activity in the modern world. Without it, our phones would lose their smarts and our favorite applications would be useless. And the more that society is reliant on digital technology, the more critical the interactions between different software will become.

How do these technologies “talk”? Using APIs — application programming interfaces.

APIs: what are they?

An API is what allows software products to connect and communicate. It lets multiple software programs exchange data according to predetermined sets of specifications. So whether you’re buying a pair of jeans on your phone, taking photos of yourself showing them off, or sharing those snaps on Instagram, various pieces of software are clicking into gear and exchanging data in the background.

To understand API usage and how APIs work, let’s break down the acronym API. 


Any software program, whether it’s an app on your phone or a web application you’re using in a web browser, needs to communicate with a wide range of technologies in order to function. 

At any given time, an application may need to connect to another application, to the Internet, or to a device. In an interaction in which data is transferred, software programs need to seamlessly connect, communicate, and carry out data exchange.

A good API example is the Google Maps API. When you search for a coffee shop online, Google Maps connects with a directory of all the local coffee shops in order to instantly show you the best possibilities for where to grab a large mocha. 


Communication between applications doesn’t just spontaneously happen on its own. If Instagram meets Spotify for a deep conversation, it’s only because the developers at each company have set up conditions for this interaction.

In API development, programmers create a set of technical specifications — the API documentation — which determines what gets communicated to other products. The documentation eliminates all potential confusion by outlining exactly what, when, and how data can pass between programs.

An API is made up of a variety of elements: services and tools the programmer can incorporate. The necessary elements are “called” or requested by the programmer. API requests are sent to endpoints and may invoke methods or subroutines. 


When people talk, information passes seamlessly between them. When someone interacts with computer software, that can’t happen without the help of an API. Instead, there’s an interface in which they can click, type, or speak in order to relay what they need to communicate. 

Software programs and computers also rely on interfaces to connect with each other. Computer programmers incorporate these interfaces, which operate more or less invisibly to end users. When one or more software programs interact, an API key, code that allows them to identify and connect with each other, is utilized.

Different APIs for different folks

APIs are categorized in various ways. Here are some of the common types of API:

Internal or private APIs

As the name implies, these are produced to facilitate data transfer for internal company use only; they can’t be accessed by third parties. However, some companies eventually take their internal APIs public.

A software organization can release an API for its product on the market so that its features and functionality can be integrated with those in other apps. The Algolia search API is one example; Algolia allows other businesses to make use of its search capabilities to improve their products.

Open, external, or public APIs

Freely available to all developers (sometimes for free, or through subscription). These asset-restricted open APIs are characterized by relatively low authentication and authorization measures.

An organization can locate an existing API to implement functionality that improves its app. For instance, a business might use Algolia’s search API to improve its document management processes. The advantage? Developers save time. They can quickly add features without needing to write every line of code or scale up their in-house team. The organization can build applications with the features and functionality that people expect, thereby maintaining an exceptional user experience, just without the extra time and labor costs. 

Composite APIs

Various data and services are combined in this type of API, which may reduce the number of API calls and overall complexity. One application: microservices, in which a single job may need data from many internal APIs.

Partner APIs

To make B2B needs easier to meet, authorized developers can access these types of APIs. 

Partner APIs typically have strong authentication, authorization, and security.

Service APIs

These APIs facilitate the integration of a service with a service provider’s inside systems.

Web APIs

These are accessible on the Web using HTTP.

How APIs work

Here are two examples of APIs being used in different business models:

With single sign-on (SSO)

When a busy dog dad signs up to utilize a dog-walking mobile application, he can choose to speed up the process of registering by tying the new app account to his Google account. This way, he doesn’t have to type in or share his personal details on a web page in multiple mobile apps. Instead, he can sign up and log in thereafter using his Google account log-in details. A back-end API makes this happen: whenever the dog owner logs in to organize the next walk, Google and the walk app act as business partners, exchanging the necessary data.

With third-party integration

An ecommerce start-up executive wants to include sophisticated search in her customer-facing storefront web application in order to compete with her rivals. She doesn’t have the resources or expertise to do the API software development to build that user interface functionality. To solve this problem, she partners with a third-party organization that specializes in search and knows how to create exceptional customer experiences. This company provides a search API that gives her team access to the technology they need and immediately improves the online search experience.

Types of API architectural style

API design dictates which information an API can share with clients and how this is done. REST (REpresentational State Transfer), SOAP (Simple Object Access Protocol), and RPC (Remote Procedure Call) are the commonly used API architectures.

  • A REST API (or “RESTful” API) is an API that follows REST guidelines and is used for transferring data from a server to a requesting client.
  • Developers use SOAP to facilitate the transmission of data across networks and to build APIs. 
  • RPC APIs invoke processes (execute scripts). In their calls, they use JSON or XML.

Why a search API matters

Sophisticated search is a requirement and customer expectation whether a company is powering internal employee systems or customer-facing experiences that drive the main interactions it has with customers. Site and app users expect to be able to navigate with ease and find what they want in as few clicks as possible.

The leading API platform for search and discovery, Algolia provides developers with a simple, robust API for utilizing search and discover capabilities. Whether you’re in ecommerce, media, health care, or some other industry, Algolia’s SaaS search can enhance your website. You can implement and quickly adapt our API to start generating eye-opening business results for all your applicable use cases.

Your developers can:

Then, you can allow your business team to get insight on how users interact with your search functionality, as well as make merchandising improvements to optimize your site experience.Our enterprise-grade search is ready to take you to the next level of digital transformation. To learn more about Algolia high-performance search and API management, as well as how to unlock the full potential of API use, contact us soon.

About the authorCatherine Dee

Catherine Dee

Search and Discovery writer

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