Wondering what the difference is between web services and APIs? Learn when to use each to build robust, scalable and efficient applications.
The online world is widely interconnected, with various systems seamlessly interacting with each other behind the scenes to provide you with a functional user experience. We might not notice it, but many of the actions we take for granted these days that seem simple on the surface typically require multiple components working in unison.
For example, let’s take an activity many of us frequently do—ordering a product on an ecommerce website. Depending on the site, every interaction you take goes through separate systems, from the moment you land on the page to the time the items arrive at your doorstep. Here’s a condensed outline of the different pieces of the puzzle that might make up a typical online shopping experience:
Unless you’re part of the team building this type of software, we usually don’t consider how things work under the hood. The ability of each of these components to communicate with each other is crucial for the entire system to function. An ecommerce site without inventory or order management systems won’t ensure you can make a successful purchase. If any of these steps break down, your experience won’t be a positive one.
This interconnectivity between systems we take for granted is powered by web services and APIs (application programming interfaces). Both of these are essential components that make up the building blocks of modern software engineering, and are the glue that lets us do everything from ordering online to watching the latest popular TV show to posting about our lives on social media. Without them, we wouldn’t have the rich interactive experiences we enjoy on the modern internet.
Despite their importance in keeping complex applications running smoothly, web services and APIs are often confused or incorrectly used interchangeably. This confusion happens because web services and APIs simplify data exchange between systems. However, they handle these tasks in distinct ways. Understanding these differences is crucial to building scalable and maintainable software products your customers love to use.
In this article, we’ll discuss web services and APIs, their differences and where each is more suitable for building applications that require interconnecting parts.
A web service is a standardized way for different systems to communicate with each other over a network. Typically, this communication happens over the internet but can also occur between networks behind a firewall or on-premises. Web services allow applications to exchange information and perform various operations using standardized protocols. These protocols help keep the exchanged data consistent, enabling smooth interaction between systems, regardless of the underlying platform.
Some of the key features that define a web service are:
Web services work best when multiple systems require a standard way to communicate with each other. An example of where web services are beneficial is with enterprise resource planning (ERP) systems. ERP systems are commonly used in larger organizations that span multiple departments, each with its own systems containing different infrastructures. Web services can provide each department a standard way to transmit information regardless of the systems they’re using.
When managing a large-scale business, a web service can simplify the overhead of juggling different systems with its standard form of communication across the board. However, web services also have some weaknesses. They’re more complex to implement and maintain than APIs due to stricter formatting when using protocols like SOAP. Communication between web services also carries some overhead since it needs extra processing to parse the information received, leading to slower response times compared to other methods.
We can define an API as an intermediary that helps different software applications communicate with each other. It allows systems to directly communicate with other systems through various methods, from standard network protocols like HTTP and REST to other methods used in modern software like WebSockets and GraphQL. APIs abstract the complexities of the underlying system and provide a simple interface for developers to interact with external services and data sources.
Among the main features that define an API are:
APIs are much simpler than web services since they allow quick integration into other systems. For instance, Stripe is a company that provides payment processing for businesses, and they offer a robust API that enables developers to integrate this service into their systems. Developers can use Stripe’s API to add payment processing or subscription management to their applications as needed and gather reports for each service. The flexibility and ease of APIs help organizations integrate with other systems quickly.
Despite their advantages, APIs also have a few shortcomings. Their flexibility often leads to inconsistent implementations when integrating with different services or even on the same service. Also, APIs can become difficult to maintain over time, especially APIs that lack proper versioning or documentation. These issues and others can increase the amount of development effort and nullify the benefits of rapid iteration.
Tools like Progress Telerik Fiddler Everywhere can help you overcome many of these issues by capturing API traffic and filtering by different criteria like URL or protocol. With these details, you can compare them to what you expect in your applications or edit them using Fiddler Everywhere’s API Composer to make developing APIs easier than ever.
If you’re like me when I began learning about web services and APIs, you’re likely thinking that web services and APIs are the same thing. On the surface, they sound almost identical—both communicate with other systems over a network, allowing for information interchange. While both services offer similar functionality, they also have important distinctions that can make a difference in how teams build applications. One way to understand these differences is using analogies from the real world.
Web services can be thought of as a set of encyclopedias. An encyclopedia contains a standardized collection of information and details in a consistent and structured format. You can pick any book from the set, and you’ll see they have a specific arrangement, making it easy to find and understand the information you seek across any volume in that set. Even today’s online version of the encyclopedia—Wikipedia—follows this pattern, where every page follows the same design and structure. If you use Wikipedia once, you’ll know how to parse that information the next time you land on another article.
Conversely, APIs can be imagined as a book from your local bookstore or library. Most books cover specific material in detail, and you can find books on a wide range of topics. Books are also structured in different ways, even when covering the same subject. For instance, cooking-related books can teach you different cooking methods or only offer step-by-step recipes for foods from a particular region of the globe. Every author writes their books in the way they believe conveys their message the best.
One way to distinguish between a web service and an API is to look at all web services as APIs, but you can’t consider all APIs as web services. Following the analogy mentioned above, encyclopedias are books, but not all books are encyclopedias. Some more practical differences between web services and APIs are:
Knowing whether web services or APIs fit your situation best while developing software is essential. Each has its strengths that serve some use cases better than others. Here are a few scenarios where a web service or API fits the bill.
Web services can help connect systems using a standardized approach to help with consistent communication across networks, which is beneficial for legacy systems or complex enterprise integrations. However, this rigidity can make web services more difficult to implement and adds some overhead during processing. APIs offer flexibility and speed, making it much easier to adopt new functionality using different communication protocols and across various platforms. This adaptability comes at the potential cost of inconsistent implementation and added maintainability costs.
With the increase of interconnected systems, understanding the differences between web services and APIs for software development is an essential skill for building robust and scalable applications. Whether you are integrating legacy systems running on distinct infrastructures or needing to quickly implement functionality across different communication methods and platforms, knowing the strengths of each will help teams build efficient and effective software.
Dennis Martinez is a freelance automation tester and DevOps engineer living in Osaka, Japan. He has over 19 years of professional experience working at startups in New York City, San Francisco, and Tokyo. Dennis also maintains Dev Tester, writing about automated testing and test automation to help you become a better tester. You can also find him on LinkedIn and his website.