REST, SOAP, and HTTP APIs: What's the difference?

Explore the differences between REST, SOAP, and HTTP APIs to choose the best fit for your project's scalability and security needs.

Application Programming Interfaces (APIs) are the critical links that allow web applications to communicate and share data. There are several options to choose from, including REST, SOAP, and HTTP APIs. And while at a high level they achieve the same goal, the differences do matter.

Understanding these differences allows developers to choose the right API for their project, ensuring applications are not just functional but also scalable, secure, and efficient.

Understanding APIs

Think of APIs as the bridges that allow your application to interact with another application — without you, the developer, ever having to “peek behind the curtain” of the other application. 

Choosing an API is a strategic decision. Each has different pros and cons, and developers must choose an API that can meet the project's specific demands, whether that's managing a high volume of requests, securing data, or providing a flexible environment for developers.

What is a REST API?

REST, or Representational State Transfer, is not a standard or specification — it is an architectural style designed for distributed systems. RESTful APIs adhere to six guiding principles that facilitate reliable, fast, and scalable web services. These principles ensure that communication protocols, such as HTTP, can be used in a simple and uniform way.

How REST APIs function

REST APIs follow six design principles:

  1. Statelessness: REST APIs operate on a stateless basis, meaning each request must carry all information needed for its execution. This approach eliminates the need for server-side sessions, as servers do not retain any data from client requests, ensuring each interaction is processed independently.
  2. Caching: REST APIs are designed to be cacheable, storing responses on the client side or an intermediary. This improves server response time. 
  3. Layered System Architecture: REST API communications may pass through various layers. The architecture should be such that neither client nor server can tell if it’s communicating directly with the end application or an intermediary.
  4. Uniform Interface: Every request for the same resource should be consistent, regardless of the request's origin. A single piece of data, like a user's email, is associated with one unique resource identifier (URI).
  5. Client-Server Decoupling: The design of REST APIs mandates a clear separation between the client and server applications, ensuring they operate independently. The client application is only required to know the URI for accessing resources and should not have any other form of interaction with the server. The server's role is to deliver the requested data without influencing the client application's behavior or structure.
  6. Code on Demand: While REST APIs typically deliver static resources, they can also provide executable code. This is considered optional and should only be used when explicitly required by the client.

Advantages of REST APIs 

REST APIs are popular for a reason — they offer advantages that make them useful for a broad spectrum of use cases. These advantages include:

Scalability: The clear separation between client and server inherent in RESTful architecture allows for straightforward scaling of products by development teams. This separation facilitates easier management and growth of applications as user demand increases.

Flexibility and portability: REST APIs enable seamless data migration between servers and simplify database modifications. This flexibility allows the frontend and backend of an application to be hosted separately, providing a significant advantage in application management and deployment.

Independence: The client-server separation characteristic of RESTful APIs supports independent development across different parts of a project. REST APIs are designed to be adaptable, conforming to the specific syntax and platforms in use, thereby enabling development in diverse environments without dependency issues.

Potential drawbacks of REST APIs

Complexity and connectivity: REST APIs can present a steeper learning curve due to web architectural nuances and require constant internet connectivity for modifications, posing challenges in offline environments.

Performance constraints: Variable performance depending on server and internet speed, coupled with inherent security vulnerabilities of HTTP and the limitations posed by statelessness, may affect certain use cases and necessitate additional security and architectural planning.

When should you use REST?

REST APIs are particularly well-suited for web services that demand scalability and performance. Their efficient handling of stateless requests makes them ideal for high-volume web applications. Qase's REST API, for example, leverages these advantages to allow 600 requests per minute and maintains the flexibility to raise that limit for enterprise organizations. The efficiency and scalability of REST APIs make them useful in modern web services, where performance and flexibility are paramount.

What is a SOAP API?

SOAP, which stands for Simple Object Access Protocol, is a protocol used for exchanging structured information across web services. It relies on XML format, and it typically operates alongside other key application layer protocols, such as HTTP and SMTP, for communication. This protocol has been a standard for web services allowing interoperability between diverse systems.

How SOAP APIs function

SOAP is designed to be independent of any specific platform or language, providing a standardized framework for the exchange of data. It operates on a request-response model, ensuring that communication between client and server applications is seamless and standardized. It is older and more established, but can be slower than newer APIs like REST.

Advantages of SOAP APIs

SOAP has remained a staple since its inception in the 90s, and for good reason. It has several advantages, including:

  • Protocol independence: SOAP can operate over any transport protocol such as HTTP, SMTP, TCP, or JMS. This independence makes SOAP a versatile choice for web service communication across various networks.
  • Built-in error handling: SOAP messages use the XML data format, which  allows for structured error messages within the SOAP envelope, enabling robust error handling and debugging.
  • Standardized protocol: As a protocol, SOAP provides a standardized structure for message formats and procedures, making it reliable for web services that require strict communication and security standards.
  • High security: The support for WS-Security makes SOAP a strong candidate for scenarios that necessitate high levels of security, including encryption and authentication.

Disadvantages of SOAP APIs

  • Complexity: SOAP's reliance on XML can lead to more verbose messages compared to other API styles, increasing the complexity and size of requests and responses.
  • Performance overhead: The bulky nature of XML messages and the complexity of the SOAP protocol can result in slower processing and larger bandwidth consumption compared to more streamlined protocols.
  • Steep learning curve: Implementing and working with SOAP APIs can have a steeper learning curve due to the intricacies of the protocol and the need for understanding WS-* standards (a collection of specifications used for web services).

When should you use SOAP?

SOAP APIs are particularly well-suited for enterprise-level web services where security measures, transactional reliability, and formal contracts are crucial. Examples include financial services and telecommunication services where the confidentiality of the data exchange are paramount. Additionally, SOAP is often used in environments that require comprehensive error handling and robust communication standards to ensure accurate and reliable data exchange.

What is an HTTP API?

HyperText Transfer Protocol (HTTP) is a well-established standard. It’s the foundational communication protocol behind the majority of our everyday interactions online. It implements some, but not all, RESTful principles. Because these APIs employ the same protocol that underpins the internet, they are a fundamental tool for web development.

How HTTP APIs function

The functionality of HTTP APIs centers around the use of standard HTTP methods — GET, POST, PUT, DELETE, etc. — to facilitate interactions between clients and servers. Each method corresponds to specific operations:

GET retrieves data from the server.

POST sends new data to the server.

PUT updates existing server data.

DELETE removes data from the server.

These interactions are stateless, meaning each request from the client contains all the information the server needs to process it and generate a response. This statelessness aids in scalability and simplifies the architecture by eliminating the need for the server to maintain any client context between requests. HTTP APIs provide a straightforward mechanism for manipulating web resources, making them ideal for a wide variety of web applications seeking efficient and direct communication capabilities.

Advantages of HTTP APIs

While HTTP APIs often share some RESTful principles, the differences give HTTP APIs different advantages, including:

  • Efficiency: By focusing on the essentials of HTTP communication, HTTP APIs can reduce the overhead associated with more complex protocols, leading to faster response times.
  • Flexibility: Without the strictures of REST, developers have more freedom to design APIs that best fit their specific needs and use cases.
  • Simplicity: HTTP APIs are easier to implement and understand, especially for developers new to API development.

Disadvantages of HTTP APIs

  • Lack of standardization: The flexibility of HTTP APIs can lead to inconsistency in design and implementation, potentially making it harder to maintain and scale the APIs over time.
  • Limited functionality: For applications that require the full spectrum of RESTful constraints for organization and scalability, HTTP APIs might fall short.

When should you use HTTP API?

HTTP APIs serve as a testament to the versatility and adaptability of HTTP itself, providing developers with a streamlined approach to web communication when the comprehensive architectural style of REST is not required. Their role in modern development highlights the ongoing evolution of web technologies to meet diverse and changing needs.

A quick glance at the differences

When evaluating REST vs  SOAP vs HTTP APIs for your project, understanding their main differences is crucial. Each API type has its own set of characteristics, benefits, and optimal use cases. 

**Feature ** REST SOAP HTTP
Type Architectural style Protocol Protocol
Data format Various, including JSON and XML XML Various, including JSON and XML
Statefulness Stateless Stateless or stateful Stateless
Transport protocol Primarily HTTP(S), but can work with others Various, including HTTP and SMTP HTTP
Security Depends on underlying transport protocol, can use OAuth, HTTPS WS-Security with comprehensive standards Security handled through HTTPS and other HTTP-level security methods
Use cases Web services, mobile applications, social networks, and any internet-based application Enterprise-level web services requiring high security and transactions (e.g., banking) Simple, quick data exchange scenarios
Performance High, due to lightweight data formats and statelessness Lower, due to complexity High, streamlined for HTTP without additional overhead

Choosing the Right API

Choosing the right API depends on the specific requirements of your project, including the desired level of security, the complexity of data being exchanged, and the scalability needs of your application. The decision should consider several crucial factors:

  • Security needs: Evaluate the level of security your application requires. SOAP’s comprehensive security standards might be necessary for projects dealing with sensitive financial data, but REST's flexibility with security protocols can also accommodate high-security needs efficiently.
  • Data format: Consider the types of data your application will handle. If your project can benefit from more lightweight data formats like JSON, REST APIs offer an advantage with their format-agnostic approach. SOAP’s reliance on XML is suitable for applications entrenched in enterprise systems.
  • Scalability: Anticipate the growth of your application. REST APIs, with their stateless operations, are inherently scalable, making them a solid choice for applications expected to experience varied loads.
  • Developer experience: Reflect on the expertise and preferences of your development team. The simplicity and wide adoption of REST can lead to quicker development cycles and easier maintenance.

Build and scale with the right API

Choosing the right API — whether REST, SOAP, or HTTP — plays a pivotal role in the development and success of web services. Each of these API architectures brings its own set of advantages tailored to meet specific project needs. SOAP offers robust security features and strict standards, preferred for enterprise-level applications where data integrity and reliability are paramount. HTTP APIs provide a more direct and efficient means of handling requests, suited for simpler or internal applications that benefit from rapid development cycles. REST is a happy medium, standing out for its flexibility, scalability, and ease of use, making it ideal for a variety of projects.

Evaluate your project's unique requirements, including security protocols, data format preferences, scalability needs, and the developer experience. Then, select an API that not only aligns with your current project goals but also supports its future growth and evolution. 

You've successfully subscribed to Qase Blog
Great! Next, complete checkout to get full access to all premium content.
Error! Could not sign up. invalid link.
Welcome back! You've successfully signed in.
Error! Could not sign in. Please try again.
Success! Your account is fully activated, you now have access to all content.
Error! Stripe checkout failed.
Success! Your billing info is updated.
Error! Billing info update failed.