Despite sounding like options on a spa menu, the SOAP vs. REST debate is a technological holy war that's about as consequential to normal humans as the proper way to arrange decorative pillows, yet somehow manages to inspire the kind of tribal devotion usually reserved for rabid sports fans or people with strong opinions about the Oxford comma (incidentally, a hill I will gladly die on).
These two application programming interface (API) technologies power most web services we use daily. APIs allow different software applications to talk to each other, much like humans use words or dolphins use clicking noises. They make it possible for your favorite apps to share data and functionality without you having to worry about how it all works behind the scenes.
Here, I'll break down REST and SOAP APIs, explain how they differ, and help you understand when to use each. Let's get started.
Table of contents:
What is SOAP API?
SOAP is a messaging protocol that provides a standardized way for different applications to exchange structured data over the internet, regardless of programming language or operating system. Developed in the late 1990s for Microsoft, it originally stood for "simple object access protocol," but the acronym was dropped in 2007 (presumably because it sounds like instructions for an art heist).
SOAP uses XML for message formatting and typically runs over HTTP (the protocol that powers the web), but it can also use other transport protocols like SMTP (email) or TCP (networks).
Every SOAP API request and response comes neatly wrapped in an XML envelope. Inside the envelope, you'll find a header with info about the message, a body with the actual data, error handling, and possibly the last known location of Amelia Earhart. It relies on web services description language (WSDL), which is basically a long-winded contract that spells out exactly how to interact with the API.
SOAP's greatest asset—according to the kind of people who read regulatory documentation for fun—is its standards. These include built-in support for encryption, authentication, message integrity, and atomic operations (either the transaction is processed completely or it fails).
Here's what a simple SOAP request might look like:
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And its response:
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As you can see, even a simple request contains quite a bit of XML markup. This structure makes SOAP messages very organized and self-descriptive but also larger than alternatives like REST, which we'll get to shortly.
Despite being older and feeling like you stumbled into a bureaucracy simulator, SOAP is still commonly used today. It's most frequently found in environments requiring stringent security and transaction reliability, like financial services, healthcare, and government.
What is REST API?
Representational state transfer (REST) is an architectural style that uses existing web standards to make APIs simpler and more intuitive. Since its introduction in 2000, it's emerged as the most popular method for developing web services. Unlike SOAP, which demands you conform to its rigid structure, REST is more of a set of best practices or a philosophy for designing networked applications. It's like feng shui for APIs.
RESTful APIs (those that follow REST principles) are all about resources and the actions you can perform on them. Resources can represent literally anything—data, objects, services, the void where your motivation used to be. Each resource is accessed via a unique URL, and you interact with it using standard HTTP methods like GET, POST, PUT, and DELETE (which sound super bossy, IMO).
For example, let's say you want to see a list of users. You would send a GET request to the URL designated for retrieving user data, such as /users. If you wanted to update an existing user's information, you would use a PUT request to a specific user's URL, like /users/123. And if you want to ruin your company's production database by accident? Congratulations, you've just sent a DELETE request to the wrong API endpoint. Well done.
REST supports multiple data formats, with JSON being the most common choice due to its simplicity and lightweight nature. However, it also supports XML, CSV, plain text, and even binary. REST is also stateless, meaning each request stands alone—just like me at networking events. This makes it great for scalability but terrible if you want transactions that remember anything beyond their immediate execution.
Here's an example of a simple REST request:
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The response might look like this:
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REST architecture powers most public APIs and mobile apps because it's simple and scalable.
What is the difference between SOAP and REST?
We've talked about SOAP and REST on their own. Now, let's see how they stack up against each other to help us figure out when it's better to use one over the other.
Protocol vs. architecture
The biggest difference between SOAP vs. REST is that SOAP is a protocol with specific standards, while REST is an architectural style with guiding principles.
SOAP requires strict adherence to its rules. It's like an NBA ref who actually calls traveling—technically correct, but it slows everything down and feels unnecessary in the modern era. However, its standardized structure can be helpful in certain contexts, like when you need to enforce strict contracts between systems.
REST provides guidelines rather than strict rules. It recommends using HTTP methods and URLs in specific ways but leaves many implementation details up to the developer.
This difference affects how rigid or flexible your API will be. SOAP's formality ensures consistency but can feel restrictive, while REST's flexibility allows for simpler implementations but may lead to inconsistencies across different APIs due to a lack of universal standards enforcing things like data format, authentication, and response structures.
Message format
SOAP messages must be formatted as XML documents with a specific structure that includes an envelope, header, and body.
REST usually rolls with JSON, but it's actually format agnostic, which is a fancy way of saying it will use any format that gets the job done.
This format difference impacts performance (JSON is smaller and faster to parse) and developer experience (many find JSON more intuitive to work with).
Communication style
SOAP focuses on actions rather than resources. Instead of asking for a thing, you're asking to do something with that thing. For example, you might see something like
GetWeatherByZipCodeorCalculateShippingCost. These method names explicitly state the action you want to take and are defined in the WSDL file.REST is resource-oriented. Instead of commands, you expose resources via URLs by slapping a standard HTTP method on it, such as
GET /weather/zipcode/02134.
This difference affects how intuitive and discoverable your API is. REST's approach often maps more naturally to the domain and is easier to understand without documentation.
Performance
SOAP messages tend to be larger due to the XML envelope structure. This can be a concern for apps with high performance requirements.
REST responses tend to be much more compact, which can be important for performance, especially in environments with limited bandwidth.
To illustrate, here's a side-by-side comparison of how the same data might be represented in SOAP vs. REST (using JSON):
SOAP | REST |
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Security
SOAP has built-in security features through an extension called WS-Security (also an excellent name for a wrestler). This allows for message-level security, including end-to-end encryption, digital signatures, and enterprise authentication.
REST primarily leans on HTTPS (SSL/TLS), which offers transport-level security. This means encryption is applied only during transport—not once it reaches its destination.
SOAP's security features are more comprehensive yet more of a pain to set up. In contrast, REST's security is more straightforward but requires additional measures (e.g., encrypting data at rest, securing APIs with OAuth) if message-level security is needed.
Error handling
SOAP uses standardized SOAP faults for error reporting, with detailed error codes and descriptions nestled in its beloved XML message structure.
REST sticks to standard HTTP status codes (400 for bad requests, 404 for not found, 500 for server errors) and asks you to try again without providing further details. That's like trying to decipher Bill Belichick's mood based on his facial expression—you might get a general idea, but good luck figuring out the specifics.
SOAP APIs provide more detailed and reliable error information but require more parsing. REST APIs offer less granular detail but are lightweight and well-suited for web services where agility is essential.
State management
SOAP can be stateful, maintaining session information between requests—like keeping your name tag on for the whole conference.
REST is stateless, treating every request as an independent transaction. Each request must contain all information needed for processing, with no dependency on previous requests.
The stateless nature of REST is one reason it's favored for large-scale web applications, while SOAP's ability to maintain state can simplify complex business processes.
When to use SOAP vs. REST
Each approach has its advantages and trade-offs. Here are some scenarios where one might be preferable over the other.
SOAP is better for:
Enterprise environments with complex security requirements
Systems that require strict contracts between services
Operations that need transactions or guaranteed delivery (e.g., stock trading, airline reservations)
Integration with legacy systems that already use SOAP
REST is better for:
Public APIs consumed by a wide variety of clients
Mobile apps where bandwidth and performance matter
Web apps, especially those using JavaScript frontends
Microservices requiring lightweight communication
Honestly, for most use cases these days, REST is the way to go. It's just more in line with how the modern web works, and it's a lot friendlier for developers to work with.
Of course, SOAP has its place, too—think serious enterprise apps where screwing up means lawsuits or jail time—but if you're building just another web or mobile app, chances are you'll be better off with REST.
What about GraphQL?
While REST and SOAP have been the dominant API technologies for many years, a newer approach called GraphQL has gained significant popularity. Born from Facebook's brain trust and released as an open source project in 2015, GraphQL offers yet another way to build APIs with some interesting advantages.
GraphQL is a query language for APIs that allows users to request exactly the data they need, rather than being force-fed a one-size-fits-all data dump like with REST or SOAP. A single GraphQL endpoint can handle multiple requests, eliminating the need for several endpoints for different data structures. This is especially useful for apps that pull from many data sources—like social media platforms or eCommerce sites.
Of course, it's not all sunshine and perfectly portioned payloads. GraphQL adds complexity on the server side because it has to process and execute queries dynamically, which means more work behind the scenes. For simpler applications with predictable data needs, this extra complexity can be overkill compared to the straightforward nature of REST.
Many major companies have adopted GraphQL, including GitHub, Shopify, Airbnb, and, of course, Meta. But before you rush off to rewrite everything in GraphQL, remember that it's still relatively new, and sometimes new isn't always better—just ask anyone who bought a Zune.
Connect all your apps with Zapier
After all this talk about APIs and protocols, you might be thinking, "This is fascinating, but I'd rather blast an email of my last hundred Google searches to my contact list than manually connect different apps." Luckily, with Zapier, you can forget everything you just learned.
Zapier makes it easy to connect and automate tasks without writing any code. With support for thousands of integrations, Zapier simplifies API interactions so you can focus on building solutions rather than managing technical complexities.
Whether you need to automate workflows, sync data, or integrate services, just tell Zapier what you want to happen, and it takes care of the rest (pun fully intended).
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