What Is An API? A Comprehensive Guide

Knock, knock! Who’s there? It’s API. API who? API, your soon-to-be best friend that’s going to help your developers reduce their coding time and drive your business towards success. If you’re seeking answers to the question: what is an API? You’re at the right place!

This article will cover the following topics:

• Introduction
• Primary Benefits
• Release Policies
• RESTful APIs
• Remote APIs
• Comparisons
• How To Create an API
• Modern APIs
• Security Best Practices
• FAQs
• Wrapping It Up

Let’s alohomora (unlock) our way into the world of APIs.

What is an API?

An application programming interface (API) enables two applications to communicate with each other. It consists of protocols and a set of definitions required to integrate systems seamlessly.

Today, businesses use API management tools to design, publish, document and analyze APIs. According to a report published by Markets and Markets, the global API management market is forecasted to grow at a CAGR of 32.9% from 2018–2023.

Are you running a health care organization? Or do you own an IT company? Regardless of your organization type, you can use API management tools to make your business operations a breeze. For instance, Apigee is an API management and analytics platform that helps you track API metrics.

How Does an API Work?

Now that we understand APIs, let’s dive deeper into their mechanism.

API usually sits between the application and the web server. The user initiates a request to the application. API is the one that decodes the request and sends it to the web server. Then, the web server responds to the request and sends results to the user.

APIs act as a middleman between apps and web servers. When customers request information through an application or website, APIs help them access data in minutes.

Common Examples of API Mechanism

To better understand the working of API, let’s go through a real-life example.

Imagine you’re at a restaurant, browsing through the menu, searching for your favorite cuisine. Once you decide, you call the waiter and place your order. Then, the waiter informs the kitchen about your order. Then, the chef prepares your meal, and the waiter serves it.

In this scenario — the menu becomes the application, the waiter the API and the chef the web server.

Still confused? Let’s place ourselves in another situation.

You want to check the weather conditions. But instead of downloading an application, you type into Google’s search box, “weather forecast today.” Google isn’t a weather prediction app. But it uses APIs to source information and presents it to you. This data is usually in the form of a snippet.

APIs work behind the scenes to enhance user experience and deliver quality results. If you are considering developing an e-commerce application for your business, don’t forget to add APIs!

Evolution of API

Change is the only constant thing in the world. And the API industry has seen a lot of changes over the years. Below we have highlighted the same.

Brief History of the Term API

The idea of the API existed even before the introduction of the term itself. We have outlined the major events that shaped the API industry below.

• 1940s: Computer scientists Maurice Wilkes and David Wheeler developed a library catalog consisting of instructions about subroutines that a programmer should follow while developing programs.
• 1951: Both Wilkes and Wheeler published a book titled, “The Preparation of Programs for an Electronic Digital Computer,” which contained information about API specifications.
• 1968: The authors of “Data Structures and Techniques for Remote Computer Graphics” used the term “application program interface” to describe the communication between a graphic program and a computer system.
• 1975: “The Relational and Network Approaches: Comparison of the Application Programming Interface” research paper introduced API to the field of databases.
• 1981: Web APIs and remote procedure calls (RPCs) helped programmers request service from remote networks and computers. These RPCs worked well with the Java language.
• 1990: Technologist Carl Malamud defined APIs as “a set of services available to programmers for performing tasks.”
• 1991: Introduction of new standards like CORBA and DCOM to expose API services.
• 2000: Roy Fielding published a dissertation, “Architectural Styles and the Design of Network-based Software Architecture,” which outlined Representational State Transfer (REST) and the idea of a network-based application programming interface.
• 2001: Tim-Berners Lee proposed the idea of semantic APIs that remodeled API as distributed and open interface instead of a software behavior interface.
• 2000–2022: XML and JSON became the most popular web APIs to exchange data digitally.

The Commercial Age

Businesses took advantage of web APIs to help customers access services from a single website. Salesforce, eBay and Amazon dominated the commercial age of web APIs.

• Salesforce: Salesforce introduced an enterprise-class, web-based API consisting of automation tools in 2000 at the IDG Demo conference. It was the first provider to launch software-as-a-service (SaaS).
• eBay: In 2000, eBay launched the eBay API portal and its developer program.
• Amazon: In 2002, Amazon introduced Amazon Web Services (AWS) to enable companies to incorporate Amazon’s features and content into their websites. It also helped third-party sites to display Amazon products in an XML format.

These companies continue to update their APIs and still dominate the commercial landscape.

Shifting To Social Networking

Today, we use social media to share information with individuals worldwide. That’s why it became vital for companies to launch APIs to help people connect apps with their social media accounts. Some of the popular companies that introduced APIs for social media are listed below:

• Facebook: It launched its development platform in August 2006. The platform enabled programmers to access Facebook users’ posts, photos, friends, profiles and events.
• Twitter: It introduced its API to prevent developers from scrapping the content and generating rogue APIs. It developed OAuth to help authorized programmers access data or perform actions on behalf of an account.
• Flickr: It produced its Restful API to enable users to embed images on social media and web pages.

Moving to the Cloud

The introduction of cloud APIs enabled multiple cloud and on-premise applications to establish a seamless connection without compromising security. Amazon noticed the importance of cloud servers and introduced its own digital storage spaces. We’ve outlined them below.

• Amazon Simple Storage (S3): Amazon introduced a basic storage service that you could access only through API. It allows customers to store and secure use cases such as data lakes, IoT devices, analytics, archives, mobile applications and websites.
• Amazon Elastic Compute (EC2): Amazon released another service called EC2 to help developers deploy applications on the cloud quickly.

Adopting Mobile Strategies

Programmers observed how people rely on mobile devices to obtain information. So they created APIs that supported mobile devices to help applications interact with each other seamlessly. Some applications that leveraged APIs were:

• Google Maps: Google released its Google Maps API to prevent programmers from reverse-engineering the JavaScript application. It provided software development kits (SDKs) to help developers embed locations into their platforms easily.
• Instagram: Instagram launched Meta for Developers platform to help users publish media, identify hashtags and mentions, and moderate comments. It also offers documentation consisting of use case guides, references and tutorials.
• Twilio: Twilio enables programmers to bulk export REST APIs to help send personalized text messages to customers, search contacts and make phone calls via cloud applications.

Connecting Next-generation Devices to the Web

As time passed by, developers came up with the idea of connecting devices like cameras, thermostats, microphones and sensors to Wi-Fi or cellular networks. API integrations turned this idea into reality. Some of the devices that use APIs are as follows:

• Fitbit: Fitbit is a wearable device that helps measure heart rate, step count and other fitness metrics. Developers can access its free web APIs to establish integrations with its services.
• Nest: Nest’s Smart Device Management (SDM) API enables programmers to connect their applications with Nest devices like cameras, thermostats and doorbells.
• Alexa: Alexa is a voice-enabled technology that helps you create to-do lists, set reminders, play audiobooks and music, and view real-time weather forecasts and news. Each function uses an API to aggregate data and provide requested information.

The API ecosystem doesn’t end with these devices. Thousands of devices and web services use API to build a connected world.

Primary Benefits

APIs have come a long way. And today, several companies use APIs to their advantage. Remember how Harry Potter used gillyweed to survive in the Triwizard task. APIs are those gillyweeds that can help your business survive in this competitive world.

There are several benefits of using APIs.

We have highlighted a few of them below.

Increase Productivity

We bet you wouldn’t want your developers to build a solution from scratch when they can use APIs and save time. With APIs, your programmers can focus on other essential activities and complete tasks quickly.

For instance, the Watson API helps you extract themes, concepts, entities, keywords and relationships from unstructured data within minutes.

According to the 2021 State of API report, the production time to develop, implement, deliver and test an API are as follows:

• Less than one hour — 4%
• Less than one day — 10%
• One day to one week — 33%
• One week to one month — 35%
• One month to six months — 16%
• More than six months — 2%

Jeff Bezos, CEO of Amazon, rightly said, “API integrations is the key to empower technical employees.”

Accelerate Sales

Continuously introducing new products or updating existing ones helps attract customers. And if you fulfill customers’ expectations, your company will surely be at the forefront. According to the State of the Connected Customer report published by Salesforce, 73% of customers expect organizations to understand their unique needs.

APIs help you create meaningful integrations, enhancing your system’s capabilities. You can also create new revenue channels, spread brand awareness and improve efficiency.

Boost Customer Experience

Today, consumers expect a hassle-free digital experience. They don’t want to jump from application to application to get the work done. API integrations help your consumers view and transfer information from one platform to another within minutes.

For instance, you launch a shopping app to increase sales. By leveraging API integrations, you can help clients share product images or descriptions with their friends via SMS, Whatsapp, Instagram or Facebook.

Encourage Innovation

Several companies publish their APIs on marketplaces and directories to help you create a cutting-edge product.

Let’s take a look at an example below.

Imagine you created an online bookstore. But you didn’t add in a media sharing functionality. You can visit online marketplaces, search for Whatsapp or other social networking APIs and add them to your website. Customers can now share their wishlists with friends with just a few clicks. This boosts customer engagement and pushes you to improve your website features.

With APIs, you can continuously develop innovative technologies that could help your business gain a competitive edge.

Release Policies

One size doesn’t fit all! The same goes with APIs too. You can make your API public if you want developers to integrate with your platform. But if you don’t wish to share resources with other programmers, you will have to restrict your API access. That’s why you need to know about API release policies. We have highlighted the same below.

• Private: You can design private APIs to improve internal services. Only your in-house developers can access these APIs.
• Partner: You can leverage partner APIs if you wish to share your services with your business partners. For example, Uber only allows approved third-party partners to use their API.
• Public: If you make your APIs public, developers can access them without any restrictions.

Note: Developers cannot access all public APIs. They might need API tokens or customer status validation to obtain them.

RESTful APIs

APIs that comply with the REST architectural constraints are known as RESTful APIs.

Based on Roy Fielding’s dissertation, there are six guiding constraints that you need to follow to call your web service RESTful.

We have listed the same below.

Client-server Architecture

An API consists of a client, server and resources. These elements should function and evolve independently to fall into the RESTful API criteria. That means the client and server will perform their functions without affecting each other.

Uniform Interface

You need to create a uniform interface to help clients interact with servers in a single language. The URL you create should load on other devices too. The four principles of the uniform interface are as follows:

• Resource-based: You need to define individual resources in requests using uniform resource identifiers.
• Resource Manipulations via Representations: When the client receives a representation, it must have enough data to alter or delete the resource (provided it has the authorization to do so).
• Self-descriptive Messages: Each message should contain enough information to help the client process data.
• Hypermedia as the Engine of Application State (HATEOAS): The API should include links for every response to help clients discover other resources easily.

Statelessness

To achieve statelessness, you should avoid storing client content on servers. You should contain it in the request as a part of query-string parameters, body, headers and uniform resource identifier (URI).

Cacheability

You should declare responses as cacheable to prevent clients from reusing incorrect data in response to future requests. Caching improves device performance and scalability.

Layered System

You should add multiple server layers to mediate client-server interactions. For example, you can use server A to deploy your API, server B to store data and server C to verify requests. These layers can assist you in load balancing, enhancing security and improving system availability.

Code on Demand

You don’t need to follow this constraint religiously because it is optional. This allows servers to send an executable code to extend the client’s functionality. But this is a huge security risk. Hackers can seriously damage your APIs if you enable the server to transmit codes. It can also result in performance degradation. So, think twice before you follow this constraint. Remember, it’s optional!

Remote APIs

Remote APIs enable you to manipulate resources outside your computer network using protocols and communication standards. Because consumers widely use the internet for communication, developers designed these APIs according to web standards.

The Java remote method invocation enables you to invoke functions existing in remote or local systems. Basically, the client-side can perform methods on an object present on the server-side.

Note: Not every remote API is a web API. But all web APIs can be remote APIs.

Different API Architectural Styles and Concepts

The world of APIs is much more than just codes. There are different architectural styles and concepts in API. Each of them consists of different features. Look at the comparison tables below to learn about them in detail.

SOAP vs. REST

Simple Object Access Protocol (SOAP) enables users to exchange information securely. SOAP uses the XML message format and receives requests via SMTP and HTTP. SOAP and REST are different from each other in a fundamental way: SOAP is a protocol, whereas REST is an architectural style.

To learn more about the differences between SOAP and REST, look at the table below.

API vs. Webhooks

APIs and webhooks might sound the same. But they are quite the opposite. We have outlined some of the significant differences in the table below.

Note: Webhooks cannot function without APIs. But APIs can perform tasks without webhooks.

SOA vs. Microservices

SOA stands for service-oriented architecture. Developers built SOAs as a response to monolithic approaches to creating applications. SOAs deliver functional, enterprise, application and infrastructure services. You can loosely couple different services into your solutions with SOAs. If you fail to describe interactions clearly, cascading changes are bound to happen throughout your application.

Programmers consider microservices as an evolution of SOAs. It enables different components to function independently — replacing, deleting or enhancing one element doesn’t affect other components. They are usually deployed on the cloud and operate using containers and virtual machines.

Take a look at the comparison table below to understand the differences between SOA and microservices.

How To Create an API

Developing an API is tedious.

If you want to create a developer-friendly and high-quality API, you should follow the steps outlined below.

Step 1: Determine Your Requirements

Before diving into the codes, you need to create a blueprint of your API design. You can list your functional (business capabilities) and nonfunctional (data security, performance and system integrity) requirements. Here are some questions that can help you determine your needs.

• Who’s your target audience?
• What do consumers expect from your product or service?
• How to incorporate your customers’ needs into your application?
• What’s the ideal response time?

Step 2: Build Your API

It’s now time to start developing your API. Some of the tasks you need to complete are as follows:

• Name and describe API.
• Make a list of operations you want your API to perform.
• Assign request and response messages to data models.
• Add security policies.
• Look into caching and rate-limiting to speed up performance.

You can use building blocks to develop your API product. Don’t forget to use the boilerplate code to design your API prototype.

Step 3: Perform API Test

Deploying an untested API is like digging your own grave. You won’t be able to detect issues that can negatively affect consumer experiences. That’s why it’s important to test your API under different scenarios. Some of the things you can do to test your API are as follows:

• Send multiple requests to API endpoints to evaluate speed and performance.
• Simulate cyberattacks to identify security vulnerabilities.
• Track the response time.
• Calculate the latency rate.

You can leverage automated API testing tools to accelerate test execution.

Step 4: Publish the API

Once you complete the testing stage, you’re ready to deploy your API. You can host it on API gateways to ensure performance, stability and security. You can also publish it on an API developer portal to increase awareness of your API.

You should also create API documentation to help programmers understand API functions and applicable use cases. Don’t forget to mention any security constraints in the API documentation.

Step 5: Evaluate API Metrics

You cannot deploy an API and forget about it completely. You need to track important metrics to identify and resolve performance issues. Some of the key metrics you should monitor are as follows:

• Operational
• Engagement and consumption
• Business

You can leverage API analytics tools to streamline your monitoring processes.

Modern APIs

Today, programmers seek APIs that are easy to implement and developer-friendly. These are called modern APIs. They are not just a generic connectivity interface. They’re a means to achieve global exposure.

Some of the modern API trends are as follows:

• The introduction of WebSocket APIs made it possible for users to interact with web servers by opening just one session — if users want to communicate with the server continuously, they don’t need to send multiple requests to the server. They’ll be able to establish a connection via a single TCP/IP socket.
• API documentation helped developers build applications that cater to specific user needs. It made it easier for programmers to connect applications with digital platforms and services.
• APIs are no longer just codes. Businesses and developers consider APIs as products. It aids companies in monetizing their services and functionalities.
  If your API only contains one feature, it won’t work in the long run. You also need to offer secondary functionalities to expand your business. For instance, if you manufacture a car that just helps you travel from destinations A–B without adding additional features, it won’t attract consumers. The same applies to API products.
• Without proper planning, it’s impossible to develop a robust application. API software development life cycle (SDLC) assists developers in planning, designing, documenting, testing and publishing APIs. It helps streamline application development processes.

The API industry’s growing rapidly. With new trends emerging yearly, developers and businesses should keep themselves updated about the same.

Security Best Practices

Because APIs transfer data through network packets, it becomes vulnerable to cyberattacks. Hackers can perform DDoS or broken access control attacks and inject viruses into your websites. Therefore, it’s important to protect confidential information to avoid data breaches.

Below are some of the best practices you can follow to keep cyber-attackers at bay.

Identify Vulnerabilities

Problems exist; so do solutions. But you cannot fix something if you have no idea what’s broken. That’s why it’s important to identify weak links in your API life cycle. You can use sniffers to spot security threats and track data spillage.

Other things you can do to spot cyber issues are as follows:

• Perform security audits.
• Protect API backends with rate limits.
• Implement an API security solution to spot Broken Object Level Authorization (BOLA).
• Analyze API traffic to view host addresses, token data points and API endpoints.

Cybercriminals can manipulate codes to compromise your website or application. It’s of paramount importance that you find and resolve security threats before they arise.

Leverage OAuth

OAuth is an authentication and authorization protocol that verifies users’ identities without exposing their login credentials. It doesn’t ask for passwords for verification purposes; instead, it uses authentication tokens.

For instance, you can grant access permissions to Candy Crush to view your Facebook profile or post updates to your timeline without sharing your password. So, if Candy Crush becomes a data breach victim, your details will remain safe and secure.

You should use OAuth to tighten authorization workflows for mobile devices and web and desktop applications.

Encrypt Data

It’s vital to encrypt API data and personally identifiable information (PII) to prevent security threats. Hackers who access encrypted data won’t be able to decipher it without a decryption key. All they’ll be able to see is a jumble of numbers, letters and characters.

You can leverage transport layer security (TLS) protocol to ensure privacy and security while communicating over the internet. You can encrypt messages, emails and VoIP using TLS.

Throttle API Requests

When the application receives multiple requests from the same user, it can result in performance degradation. API throttling helps limit the number of API requests made from the same client. It indicates to the system that the motive of the request is to slow down the webpage. As a result, it displays an error status code: 429 on the website.

Throttling also helps you protect systems from DDoS attacks. It assists you in ensuring data security and preventing malicious attacks.

Use an API Gateway

An API gateway is a middleman between the client and backend services. It’s an API management tool that helps you intercept requests and perform necessary actions. Common features include rate limiting, analytics, routing, monitoring, authentication and billing.

Adopt a Zero-trust Approach

Earlier, users connecting from external network perimeters weren’t trusted. But due to an increase in insider threats, you can’t trust internal or external connections. It’s best to adopt a zero-trust philosophy to tighten your network security measures. It allows you to verify users’ identities and avoid cyberattacks.

FAQs

How Can You Secure REST APIs?

An insecure API is vulnerable to cyberattacks. That’s why it’s important to implement security measures to safeguard your APIs. You can secure REST APIs using:

• Authentication Tokens: You can verify users’ identities while making the API call. For example, if the individual wants to log in to their email account, they’ll have to authenticate via a password. Nowadays, businesses use the two-factor authentication method to protect confidential information.
• API Keys: If you want to verify an application or program, you should use API keys. They help you identify access rights and monitor API usage.
• Password Hash: You can hash your passwords using encryption algorithms like SHA-2 and PBKDF2. Password hashing turns passwords into strings of letters to keep hackers from decoding them.

What Are Some of the Tips To Write API Documentation?

Creating API documentation is of vital importance. It helps other developers configure APIs correctly. To write good API documentation, you should:

• Use coding examples to explain functions clearly.
• Describe features in simple language.
• Create a glossary highlighting complex terms.
• Try itemizing the guide.
• Keep the tone conversational.
• Cover problems that your API can solve.

You can leverage documentation tools to accelerate your documentation processes. But documents generated using these solutions can become wordy and might require editing. You should update your documentation regularly to maintain data accuracy.

What Is an API Endpoint?

An API endpoint is a final touchpoint where API communication ends. Let’s look at an example below.

Joe and Jane are talking to each other on the phone. When Joe says, “Hello,” his words reach Jane. So, in this case, Joe becomes the client, and Jane becomes the endpoint.
Similarly, when you make an API call, the server response you receive becomes the endpoint.

API endpoints specify the exact location of resources.

For example, suppose you want to access a user’s recent media on Instagram. In that case, you can use the Instagram Graph API’s user endpoint code:

GET https://api.instagram.com/users/self/media/recent

API endpoints are of prime importance for two reasons — security and performance. Because an API can have multiple endpoints, you need to secure it to improve the performance of your application. You can employ an endpoint security solution to protect your network from malware, viruses and other cyber threats.

What’s GraphQL?

GraphQL is a query language that helps you accelerate API performance. It provides an intuitive syntax that assists you in describing data interactions. With GraphQL, you’ll receive exact results for your request and no more. That means clients don’t have to fetch over to find information. You can change data fields without affecting existing queries.

How Can You Find New APIs?

You can find new APIs through API marketplaces or directories.

An API marketplace is like an online store dedicated to developers. You can find code snippets, standardized documentation and more.

An API directory is a repository of available APIs. You can filter APIs based on your preferred category.

Wrapping It Up

We hope now you won’t have to ask who API is when it knocks on your door. APIs are changing application interactions all over the world. From machine learning to artificial intelligence, APIs are powering technologies to do their best and improve network connectivity.

You can implement API management, analytics and security solutions to make your software development process more efficient.

We hope we were able to provide a detailed answer to your question: what is an API? Is there anything important that we missed?