What is an API?

Are you confused about what APIs are and how they can be used? If so, you’re not alone. In this article, we’ll dive deep into the basics of an API to get you started.

Are you confused about what APIs are and how they can be used? If so, you’re not alone.

API stands for Application Programming Interface and it’s a great way to interact with different services without leaving your system. Learning more about them is essential knowledge in today’s world of technology, and in this article, we’ll dive deep into the basics of an API to get you started.

Unpacking APIs

In today’s world of software development, APIs have become a crucial component that enables different applications and services to talk with each other seamlessly. APIs, provide a standardized way for different software components to communicate with each other, making it possible for separate services and applications to combine, exchange data, and interact with each other in real-time. From booking a ride with Uber, to ordering food with Deliveroo, or sharing photos on Facebook, APIs are working behind the scenes to make the user experience seamless and efficient.

Without APIs, these applications and services would not be able to communicate, making life a lot more difficult. The importance of APIs goes way beyond just enabling different applications to communicate with each other; it also allows developers to focus on building their own application's unique features and user interfaces without the hassle of building everything from scratch. With APIs, developers can easily integrate pre-built functionalities and services into their applications, freeing up time and resources to deliver faster and better software products. It's fair to say that APIs are the unsung heroes of modern software development.

Core Functions of an API

Abstraction and Encapsulation

When it comes to programming, one of the main benefits of using APIs is the way they abstract underlying complexities and encapsulate functionalities.

This means that the consumer of the API doesn't have to worry about all the technical details and intricacies that go into making a particular function work. Instead, they can simply call the API and expect to receive the desired outcome. This not only saves a considerable amount of time and effort but also helps to ensure consistency across different applications and systems.

Essentially, an API acts as a contract between the provider and the consumer, outlining exactly what each party will do to achieve a certain outcome. By doing so, APIs make it easier for developers to create powerful and effective software in a more streamlined and efficient way.


Communication between diverse systems has become increasingly important. APIs, or Application Programming Interfaces, have played a crucial role in enabling this communication to happen, regardless of language or platform.

APIs allow different systems to interact with each other in a consistent way, meaning that software developers can build applications on different platforms and still communicate with one another. They make it possible for complex systems to work together seamlessly and efficiently. In short, APIs represent a powerful tool for ensuring that communication between diverse systems is possible, enabling innovation and collaboration on a global scale.

Reusability and Modularity

When it comes to software development, efficiency and speed are key. That's why APIs have become so integral to modern programming. Not only do APIs allow different applications to communicate with each other, but they also promote code reusability and modular development.

By breaking functions and features into smaller components developers can create components that can be used and reused in various contexts with minimal modifications. This approach streamlines the development process and reduces the risk of errors. Also, with APIs, you can ensure that applications are highly adaptable to changing requirements as it's easy to update and improve upon individual components without affecting the rest of the codebase. It's no wonder that APIs have become such a popular tool in software development today.

Anatomy of an API Call

Making an API call may seem like a daunting task, but it is a highly important process for many developers.

The first step is to create a request, which is essentially a message sent to a server requesting data or a certain action. This request is sent using a specific format, such as JSON or XML.

Once the request is sent, the server will process it and send a response back to the client. This response will include the requested data or action, usually in the same format as the request. It is important to note that API calls may also include authentication and error handling processes to ensure security and smooth functioning.

You can then make additional API calls or perform other actions in your application based on the results of the initial API call.

Working with external APIs can be a finicky and unpredictable process. You can never quite tell how they'll behave, which makes it more important to follow best practices and handle errors considerately. Doing so goes a long way in ensuring that your application remains reliable and robust in its interactions with these APIs. It might seem tedious at times, but the little extra effort of designing around error scenarios and sticking to best practices can save you plenty of headaches down the line. Ultimately, it's all about creating a smooth and seamless experience for your users, and taking these steps is a key part of making that happen.

Types of APIs: A Closer Look

The most common web API’s

Open APIs

Open APIs are publicly available and can be easily integrated into third-party applications. This means that if you have an idea for an app or service that uses a company's data, you can easily access it through an open API. The best part about open APIs is that they're often free to use and can save you a lot of time and money on development costs.

Internal APIs

Internal APIs are a critical component for any business that relies on multiple apps and systems to run an efficient operation. These APIs enable different programs within the company to communicate and share information in real-time without any missing links.

Partner APIs

Unlike traditional APIs that offer unlimited access to developers, partner APIs are more restricted, granting access to only specific data and resources. This prevents partners from accessing sensitive or confidential information that may not be necessary to their application or integration. These APIs function as a bridge between the company and its partners, providing access to key functionality while maintaining the security of the system.

Types of API Protocols


REST, short for Representational State Transfer, is a set of architectural principles that dictate how web services should communicate. RESTful APIs follow these principles to keep interactions between clients and servers stateless, meaning they don't store any information from previous transactions. Instead, RESTful APIs use HTTP methods such as GET, POST, PUT, and DELETE to fetch, create, update, and delete resources. This makes it easier for developers to build robust applications that can handle a large volume of requests.


SOAP - Simple Object Access Protocol, is an API that's been around for quite some time, but it remains widely used in many industries. Essentially, it allows for the transfer of data between applications via XML, making it easier to integrate dissimilar systems and facilitate communication. SOAP can be seen as a reliable, established technology for building web services, and while there may be newer alternatives out there, it remains an important tool for many developers and organizations.

GraphQL APIs

GraphQL is an alternative to REST that offers more flexibility when it comes to data retrieval. With REST, you often have to make multiple requests to retrieve all the information you need. But with GraphQL, you can get everything you need with just one query. This makes it a fantastic option for applications with complex data needs. It also offers more control to the client when it comes to deciding what data is returned, which is a huge benefit. Overall, if you're looking for a more flexible and efficient way to retrieve data with APIs then GraphQL is worth checking out.

Webhook API

Webhook APIs have become essential tools for developers and businesses alike. The power of webhooks is in their ability to send real-time notifications and data between different applications and services. They enable seamless communication and integration between systems, improving productivity and efficiency.


GRPC is a high-performance and open-source remote procedure call (RPC) framework designed specifically for building fast APIs on top of modern protocols and architectures. It is rapidly gaining popularity among developers and businesses alike because of its speed and simplicity. With GRPC, developers can easily build scalable and reliable systems that are easy to debug and maintain. The framework uses efficient binary protocols like Protocol Buffers for data serialization, which allows it to transmit data much faster with minimal overhead. Furthermore, it supports multiple programming languages, making it an excellent choice for cross-language development. In summary, GRPC is a modern solution that is easy to use and provides high performance for building APIs.

Benefits and Applications of APIs

Third-Party Integrations

By leveraging APIs, businesses can connect with multiple systems and services seamlessly. With this integration, businesses can easily access data and functionalities from different systems without having to use different interfaces or manually update information in various software systems. For example, many eCommerce platforms use APIs to connect with payment processors and shipping providers, streamlining the order fulfillment process. APIs also enable developers to build third-party apps that integrate with popular services like social media platforms or email clients. This enables the business to connect with more people effortlessly and share information seamlessly across multiple channels.

Data Retrieval and Manipulation

APIs play a key role in facilitating data retrieval and manipulation activities such as data analysis, cloud computing, and mobile application development, all in a secure, reliable, and efficient way. APIs serve as a bridge that connects a requester to a remote server or database, making it possible for the requester to retrieve and manipulate the requested data. An API acts as a mediator between two platforms and ensures that data is exchanged securely. It offers a set of rules and conventions that developers must follow when building and designing software, making it easy to integrate with other applications.

Customization and Extension

With APIs, developers have the power to take existing software and make it even more powerful. The ability to customize and extend software is what sets API development apart from traditional development. By leveraging APIs, developers can add new functionality and features to existing software, making it more versatile and efficient. With the growing popularity of APIs, the possibilities are virtually endless. So, if you're a developer looking to enhance your software development skills, understanding, and utilizing APIs is a must.

Efficiency and Collaboration

APIs have made a tremendous impact on software development in recent years. One of the biggest benefits of utilizing APIs is that they allow teams to work on different components of a project simultaneously, increasing productivity significantly. This enables developers to work more efficiently, reducing development time and freeing up time for more critical aspects of the project. By working on different components of the project simultaneously, teams can also easily collaborate with one another, sharing data and insights to produce better results.

API Documentation and Best Practices

Documentation Importance

Clear and comprehensive API documentation should always be a top priority. Not only does it improve the ease of understanding for developers to implement API functionality, but it also reduces the instances of unnecessary technical support requests. Nothing is more frustrating than finding out that instructions are missing from a crucial step in the process, or worse, when it's incoherent and tangled up. With detailed documentation, developers can function independently and confidently collaborate with other teams. Dedicating time and effort into the documentation process can result in countless future benefits, including more satisfied developers, elevated quality of code, and a stronger community. Ultimately, APIs are meant to facilitate communication between applications, and with the correct documentation, development teams can efficiently create software that solves problems with clarity and precision.

Key Elements in API Documentation

Endpoint Details

When it comes to API documentation, endpoint details are an essential element that can't be overlooked. Endpoints are, in essence, the gateways that connect your application with the API functionality that it needs to access. So, it's essential to have a clear understanding of which endpoint connects to which specific functionality. This will help programmers navigate the API do87cumentation with ease and have a thorough understanding of how to make their apps work as efficiently as possible. It's also an excellent way to avoid potential errors and mistakes when coding.

Request and Response Formats

By specifying data formats, you can ensure that all parties involved in the communication process are on the same page and that the transfer of information is smooth and efficient. This is particularly important when working with APIs, which require data to be formatted in a specific way to function correctly. By clearly defining the formats and providing examples, developers can save time and avoid frustrating errors. At the end of the day, clear and accurate communication is paramount to the success of any project, and carefully considering the request and response formats is one way to achieve it.

Authentication and Authorization

Out of the numerous critical elements in an API documentation, authentication and authorization must be given top priority. Security measures like API keys and tokens using OAuth2 play a significant role in ensuring the security of your API. They help in identifying and restricting access to your API from unauthorized applications. Therefore, they ensure that only authorized applications and users get access to your services. By prioritizing authentication and authorization, developers can take necessary measures to ensure their API is safe and secure; hence, enhancing the overall user experience.

Error Handling and Troubleshooting

In the world of APIs error messages and codes play a critical role in communication between servers and clients. Simply put, an error message informs a client that something went wrong while sending a request to a server. Likewise, an error code indicates the type and severity level of an error that occurred. These messages and codes are essential in troubleshooting and debugging issues that may arise when interacting with web applications or software. The successful implementation of proper error messages and codes ensures better communication between client and server, leading to smoother and more efficient application development. Therefore, it is essential to include them in API responses for reliable application development.

Mailosaur’s Email and SMS Testing API

Using the Mailosaur API, you can write automated tests for the email and SMS messages your product sends. Check out our API documentation here to find out how the Mailosaur API lets you test email using a simple REST API. If you have any questions contact us today, or try it out for yourself with our 14-day FREE trial.