SOAP vs REST APIs: The Ultimate Showdown

SOAP and REST are two major approaches to building APIs, each with unique strengths.

• SOAP: A protocol designed for enterprise-grade integrations, relying on XML for strict structure and robust security (WS-Security). Best for industries like finance and healthcare where data integrity and compliance are critical.
• REST: An architectural style using HTTP methods and supporting flexible data formats like JSON and XML. Known for its simplicity, speed, and scalability, making it ideal for mobile apps, web services, and public APIs.

Quick Comparison:

If you want strict security and transactional reliability, go with SOAP. For faster, lightweight, and scalable solutions, REST is the better choice.

Basic Concepts and Structure#

SOAP Fundamentals#

SOAP operates as an XML-exclusive protocol with a rigid message structure, consisting of an Envelope, an optional Header for metadata, and a Body for the payload. This setup is ideal for enterprise-grade applications where precise message handling is critical. Services in SOAP are defined through WSDL (Web Services Description Language). One of SOAP's strengths is its transport independence, allowing it to work over HTTP, SMTP, or other protocols, making it a reliable choice for complex enterprise environments. Now, let's look at REST to see how its design differs.

REST Basics#

REST relies on standard HTTP methods like GET, POST, PUT, and DELETE, and it supports various data formats. JSON is often the preferred format due to its lightweight structure and simplicity. REST follows a stateless architecture, meaning each request must include all the information needed for processing. This eliminates the need for server-side state management, enhancing scalability and simplicity.

"The main difference is that SOAP is a structured protocol, while REST is more flexible and less defined." - Anna Fitzgerald [1]

Structure Comparison#

REST's lightweight messages and caching support make it an efficient choice for web applications. On the other hand, SOAP's structured approach includes built-in ACID compliance (Atomicity, Consistency, Isolation, Durability), which is crucial for applications requiring strict transactional integrity. In essence, SOAP focuses on operations and structure, while REST emphasizes flexible, resource-driven management - an important factor when scaling modern applications.

Speed and Implementation#

Speed Tests#

Performance testing highlights clear differences in how quickly messages are processed. REST benefits from its lightweight nature, using JSON for smaller message sizes, which reduces bandwidth usage and allows for faster responses compared to SOAP's XML-based messages [2]. This speed advantage makes REST a better choice for systems that need to scale effectively.

System Growth#

REST's stateless design is a game-changer for scalability. Because each request contains all the information needed, servers don't have to store session data, which lowers memory usage and simplifies load balancing across multiple servers [3].

Development Time#

The choice between REST and SOAP doesn't just affect scalability - it also impacts how quickly and easily developers can build and maintain systems. REST's straightforward design and reliance on standard HTTP methods typically lead to faster development cycles [3]. Here's a side-by-side comparison of key development aspects:

These differences show why REST is often the go-to choice for modern web development.

Technical Metrics#

REST's popularity is no coincidence - over 70% of public APIs now use this approach [4]. Several technical strengths explain this trend:

1. Message Processing: REST's smaller payloads allow for faster data handling [2].
2. Resource Utilization: Its stateless nature reduces the strain on server memory and processing power [2].
3. Caching Efficiency: Built-in caching features lighten server loads for frequently accessed data [2].

For high-traffic applications, these advantages make REST an obvious choice when speed and scalability are top priorities [2].

Security Features#

SOAP Security Tools#

The WS‑Security framework in SOAP enforces strict rules for message integrity, authentication, and encryption. According to recent data, API attacks rose by 681% in 2022, with companies facing an average loss of $2.4 million [5].

WS‑Security provides three main layers of protection:

• Message Encryption: Relies on X.509 certificates to encrypt messages end-to-end.
• Digital Signatures: Ensures the message's authenticity and protects against tampering.
• Identity Tokens: Delivers strong user authentication and authorization mechanisms.

REST Security Methods#

REST relies on HTTPS for transport-level security and offers several authentication methods tailored to different needs [2].

When implemented correctly, these methods comply with U.S. regulatory requirements.

U.S. Standards#

Beyond these security measures, U.S. standards impose specific compliance requirements. Both SOAP and REST can meet these standards, though SOAP's ACID compliance and WS‑Security often make it a better fit for industries like finance and healthcare [2][3].

Here’s how compliance applies across key industries:

• Financial Sector
  SOAP's ACID compliance ensures reliable and consistent transactions, making it ideal for banking systems where data integrity is critical [2].
• Healthcare Industry
  SOAP's robust end-to-end security helps safeguard sensitive patient data. REST, while effective, may require additional measures to reach similar levels of protection [3].
• Enterprise Systems
  For organizations managing sensitive information, SOAP's standardized security simplifies compliance audits, streamlining processes in heavily regulated U.S. industries.

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Video Explainer: Understand the Difference Between SOAP and REST APIs#

Just so you have a different perspective, here's a comparison that the team at Smartbear put together:

Common Applications#

Here's a closer look at where SOAP and REST APIs perform best, based on their technical strengths and security features.

When to Use SOAP#

SOAP is ideal for organizations needing high security and dependable messaging. Its WS-Security framework, guaranteed message delivery, and built-in error handling make it a strong choice for critical tasks [6]. For example:

• Banking: SOAP ensures secure interbank transfers, protecting sensitive financial data.
• Telecommunications: Secure messaging makes it a reliable option for this sector.
• Municipal Systems: SOAP's predictable and secure operations are well-suited for city infrastructure.

When to Use REST#

REST's lightweight design is perfect for dynamic, modern applications. It dominates web development, with 83% of APIs using this architecture [8]. Here’s what makes REST shine in specific scenarios:

For more details, check out the industry-specific breakdown below.

Application Guide#

This table connects industry needs with the best API architecture:

"In general, you should use REST for simpler, more flexible, and scalable web services, and SOAP for standardized, protocol-based communication requiring high security and transactional reliability." - Terence Bennett, CEO of DreamFactory

Tools for Managing SOAP & REST APIs#

Zuplo's API gateway offers a robust solution for managing both REST & SOAP APIs. Operating across more than 300 global data centers, it delivers a typical latency of less than 50ms [4]. Zuplo's API gateway is fully programmable, allowing you to write and deploy custom functions to scale controls across your entire API surface - check it out:

Whether you decide to build with REST, SOAP, or both - check out Zuplo to secure your API, and provide a Stripe-quality developer experience for your customers!

FAQs#

What makes SOAP a better choice than REST for industries with strict compliance needs?#

SOAP APIs are well-suited for industries with strict compliance requirements because they offer robust security features like WS-Security, which ensures end-to-end protection for transmitting sensitive data. This makes them ideal for applications in sectors like finance, healthcare, and government.

Additionally, SOAP provides built-in reliability with advanced error handling and supports formal contracts through WSDL (Web Services Description Language). These features help maintain consistency, enforce strict standards, and ensure seamless communication between systems, which is critical for compliance-heavy environments.

Why does the stateless design of REST APIs make them more scalable and efficient for web applications?#

The stateless nature of REST APIs ensures that each request from a client contains all the information needed to process it. This eliminates the need for servers to store session data, making it easier to distribute requests across multiple servers. If traffic increases, new servers can be added seamlessly without worrying about shared state or session management.

This design also improves performance since servers can process requests independently, reducing complexity and potential bottlenecks caused by maintaining state. As a result, REST APIs are well-suited for large-scale, high-traffic web applications.

When is SOAP's built-in WS-Security a better choice than the security methods used in REST APIs?#

SOAP's WS-Security is particularly useful in scenarios where end-to-end security is critical, especially when data passes through multiple intermediaries. Unlike REST, which typically relies on transport-layer security like HTTPS, SOAP embeds security features directly into the message, such as digital signatures and encryption.

This approach is ideal for handling sensitive data or ensuring message integrity in environments where messages may be transformed or stored. For example, industries like healthcare and finance often prefer SOAP for its robust security capabilities when dealing with confidential information.