REST API vs SOAP API: What’s the Difference?

Modern applications rarely operate completely on their own.

A mobile app may need customer information from a server. An e-commerce website may connect with a payment service. Meanwhile, business software may exchange information with CRM, ERP, logistics, or accounting systems.

APIs make these connections possible.

Two well-known approaches for building web-based integrations are REST APIs and SOAP APIs.

REST and SOAP can both allow software systems to communicate. However, they follow different architectural approaches and are commonly used for different types of integrations.

REST stands for Representational State Transfer.

SOAP stands for Simple Object Access Protocol.

In simple terms:

REST API: A flexible architectural approach commonly used for web and mobile services.

SOAP API: A standardized messaging protocol with strict rules and built-in enterprise specifications.

Therefore, REST is common in modern web, mobile, SaaS, and public API development. SOAP, in contrast, remains relevant in enterprise environments where formal contracts and specific messaging standards are important.

In this guide, we will compare REST vs SOAP, including architecture, data formats, performance, security, error handling, development complexity, scalability, and common business use cases.

What Is a REST API?

REST is an architectural style for designing networked applications.

A REST API typically organizes information around resources.

For example, an e-commerce system may provide resources such as:

• Customers
• Products
• Orders
• Payments
• Categories

Each resource can be accessed through an endpoint.

For example:

/customers

/products

/orders

Therefore, developers can interact with business data through clear resource-oriented URLs.

REST API Example

Imagine an online store needs information about order number 1050.

A REST API might use a request similar to:

GET /orders/1050

The server could return information about that order.

For example:

{
  "id": 1050,
  "status": "shipped",
  "total": 249.99
}

Therefore, the application can request only the resource it needs.

In addition, REST APIs commonly use JSON because it is lightweight and widely supported.

What Is a SOAP API?

SOAP is a messaging protocol for exchanging structured information between systems.

Unlike REST, SOAP defines a more formal messaging standard.

SOAP messages use XML.

For example, a SOAP message contains an XML envelope that defines the structure of the request or response.

Therefore, SOAP integrations generally follow stricter specifications.

SOAP is commonly associated with enterprise systems and integrations that require formal service contracts or specific standards.

SOAP API Example

Imagine a business system needs information about a customer account.

A simplified SOAP request could look like this:

<soap:Envelope>
  <soap:Body>
    <GetCustomer>
      <CustomerId>1050</CustomerId>
    </GetCustomer>
  </soap:Body>
</soap:Envelope>

The server processes the message and returns another structured SOAP response.

Therefore, both systems communicate through an agreed XML message format.

REST API vs SOAP API: Quick Comparison

Feature	REST API	SOAP API
Type	Architectural style	Messaging protocol
Common data format	JSON	XML
XML support	Yes	Required
HTTP support	Common	Common
Other transports	Not the typical REST model	Can support other transports
Message structure	Flexible	Strictly defined
Development complexity	Usually lower	Usually higher
Payload size	Often smaller	Usually larger
Performance overhead	Often lower	Often higher
Service contract	Can use OpenAPI or other definitions	Commonly uses WSDL
Built-in standards	Fewer protocol-level standards	Extensive WS-* standards
Caching	Supported through HTTP	Less commonly used this way
Stateless design	Core REST constraint	Depends on implementation
Web/mobile APIs	Very common	Less common
Enterprise integrations	Common	Still used
Public APIs	Very common	Less common
Formal transactions	Application dependent	Standards are available
Best fit	Modern web and application APIs	Specific enterprise integration requirements

Therefore, REST generally emphasizes simplicity and web architecture. SOAP emphasizes standardized messaging and formal contracts.

The Main Difference: Architectural Style vs Protocol

One of the most important differences is that REST and SOAP are not exactly the same type of technology.

REST is an architectural style.

SOAP is a protocol.

Therefore, REST provides architectural principles rather than defining one mandatory message format.

SOAP, in contrast, specifies how messages should be structured.

As a result, SOAP implementations tend to follow more rigid rules.

REST Uses Resources

REST APIs commonly organize functionality around resources.

For example:

/customers

/orders

/products

Developers then use HTTP methods to perform actions on those resources.

Therefore, the URL usually identifies the resource while the HTTP method describes the requested operation.

SOAP Uses Operations

SOAP services are often organized around operations.

For example:

GetCustomer

CreateOrder

UpdateAccount

ProcessPayment

Therefore, the service contract defines which operations are available and what information each operation expects.

This approach can work well when two enterprise systems need a clearly defined communication contract.

HTTP Methods in REST

REST APIs commonly use standard HTTP methods.

For example:

GET — Retrieve information

POST — Create a resource

PUT — Replace or update a resource

PATCH — Partially update a resource

DELETE — Remove a resource

Consider a customer API.

GET /customers/25

could retrieve customer 25.

Meanwhile:

DELETE /customers/25

could request removal of that resource, subject to application rules.

Therefore, HTTP methods communicate the intended action.

SOAP Operations

SOAP does not rely on HTTP methods in the same resource-oriented way.

Instead, the SOAP message typically identifies the requested service operation.

For example:

CreateCustomer

GetCustomer

UpdateCustomer

CancelOrder

Therefore, developers work with defined service operations rather than primarily modeling interactions as HTTP resources.

REST and JSON

JSON is commonly used with REST APIs.

For example:

{
  "customerId": 501,
  "name": "Alex",
  "status": "active"
}

JSON is relatively compact and easy for modern applications to process.

Therefore, it is popular for web and mobile APIs.

In addition, JavaScript applications can work naturally with JSON data.

SOAP and XML

SOAP uses XML for its messages.

For example:

<Customer>
  <CustomerId>501</CustomerId>
  <Name>Alex</Name>
  <Status>active</Status>
</Customer>

XML provides a highly structured document format.

However, XML messages can be more verbose than equivalent JSON payloads.

Therefore, SOAP can involve greater message overhead.

Payload Size

Payload size can affect network usage and processing.

A REST API using JSON can often represent information with relatively little markup.

SOAP messages include XML structure and the SOAP envelope.

As a result, equivalent SOAP messages may be larger.

Therefore, REST is often attractive for mobile applications and high-volume web APIs.

However, payload size is only one factor in overall application performance.

REST API Architecture

A simplified REST integration might look like:

Mobile App

↓

HTTPS Request

↓

REST API

↓

Application

↓

Database

The mobile app requests a resource.

Next, the API processes the request.

Finally, the server returns a response.

Therefore, REST fits naturally into modern web application architecture.

SOAP API Architecture

A simplified SOAP integration may look like:

Enterprise System

↓

SOAP XML Message

↓

SOAP Service

↓

Business Logic

↓

Enterprise Database

The requesting system creates a message based on the service contract.

Next, the receiving service validates and processes it.

Finally, a structured SOAP response is returned.

Therefore, SOAP can provide a formal interface between enterprise applications.

REST and HTTP

REST is strongly associated with HTTP.

For example, REST can use:

• URLs
• HTTP methods
• Status codes
• Headers
• Caching

Therefore, REST can take advantage of existing web infrastructure.

This is one reason REST became popular for internet-based APIs.

SOAP and Transport Protocols

SOAP is not limited conceptually to HTTP in the same way REST commonly is.

SOAP messages can be used with different transport mechanisms.

However, HTTP and HTTPS are widely used in real-world SOAP web services.

Therefore, businesses should evaluate the actual implementation rather than assuming a specific transport.

REST API Responses

REST APIs commonly return JSON responses.

For example:

{
  "orderId": 1050,
  "status": "processing"
}

The API can also use standard HTTP status codes.

For example:

200 — Request successful

201 — Resource created

400 — Invalid request

401 — Authentication required

404 — Resource not found

500 — Server error

Therefore, REST APIs can use standard web conventions for communicating results.

SOAP Responses

SOAP responses use structured XML messages.

If the operation succeeds, the service returns the expected response message.

However, when an error occurs, SOAP can return a SOAP Fault.

Therefore, errors can follow a standardized SOAP structure.

This provides a formal way for SOAP services to communicate failures.

Error Handling

REST commonly combines application error responses with HTTP status codes.

For example:

404 Not Found

could indicate that a requested resource does not exist.

In addition, the response body may contain more information.

SOAP uses SOAP Fault messages for protocol-level error communication.

Therefore, both approaches provide error handling, but they follow different models.

REST and Statelessness

Statelessness is an important REST constraint.

Each request should contain the information necessary for the server to understand it.

Therefore, the server should not depend on conversational state from an earlier request in order to interpret the current request.

For example:

Request 1 → Get Product

Request 2 → Create Order

Each request is processed independently according to the API design.

As a result, stateless services can be easier to scale across multiple servers.

SOAP and State

SOAP itself does not require the same REST architectural constraint.

Therefore, SOAP-based services can be designed around different interaction patterns.

However, many SOAP web services are also implemented without maintaining conversational state between normal requests.

As a result, actual behavior depends on service design.

API Contracts

API contracts define how applications communicate.

REST APIs can use documentation standards such as OpenAPI.

For example, an API definition can describe:

• Endpoints
• Methods
• Parameters
• Request bodies
• Responses

Therefore, developers can understand how to integrate with the service.

SOAP commonly uses a more formal service contract through WSDL.

What Is WSDL?

WSDL stands for Web Services Description Language.

It describes a SOAP web service.

For example, WSDL can define:

• Available operations
• Input messages
• Output messages
• Data types
• Service endpoints

Therefore, development tools can use the service description to generate client code.

This formal contract is one reason SOAP has historically been popular in enterprise integration.

REST and OpenAPI

REST APIs commonly use OpenAPI specifications for documentation and tooling.

For example, an OpenAPI definition can describe:

GET /customers/{id}

It can also define expected parameters and responses.

Therefore, developers can generate documentation, test requests, and sometimes create client libraries.

However, OpenAPI is separate from REST itself.

A REST API can exist without an OpenAPI specification.

Development Complexity

REST APIs are often simpler to develop for common web use cases.

For example, developers can work with:

• HTTP
• JSON
• URLs
• Standard status codes

Therefore, the learning curve can be relatively straightforward.

SOAP introduces additional concepts such as XML envelopes, WSDL, and potentially WS-* specifications.

As a result, SOAP integrations can require more specialized knowledge.

Performance

REST APIs are often considered lightweight.

For example, JSON payloads can be smaller than equivalent SOAP XML messages.

Therefore, less data may need to be transferred and parsed.

SOAP messages generally contain more XML structure.

As a result, they can create additional processing and bandwidth overhead.

However, actual performance also depends on network latency, database queries, application logic, caching, infrastructure, and payload design.

Therefore, API style alone does not determine performance.

Caching

REST can work naturally with HTTP caching.

For example, a product catalog endpoint may return information that does not change frequently.

Therefore, caching can reduce repeated server processing.

SOAP services can also use caching at different infrastructure layers.

However, caching is not as central to the SOAP messaging model.

As a result, REST is often easier to align with standard web caching behavior.

Scalability

REST’s stateless architecture can support horizontal scaling.

For example:

API Server 1

API Server 2

API Server 3

Requests can be distributed across servers.

Therefore, REST works well for many large web platforms.

SOAP systems can also scale.

However, scalability depends on the service architecture rather than SOAP alone.

Therefore, either approach can support enterprise-scale workloads when designed correctly.

REST API Security

REST APIs commonly use HTTPS for transport security.

Authentication and authorization can use approaches such as:

• API keys
• OAuth
• Access tokens
• Other application-specific mechanisms

Therefore, REST security is usually implemented through several web and application standards.

However, developers need to design those controls correctly.

REST itself does not provide one complete built-in security specification.

SOAP API Security

SOAP can use HTTPS as well.

In addition, enterprise SOAP environments may use specifications such as WS-Security.

These standards can support requirements involving message-level security.

Therefore, SOAP can be useful in environments that require specific WS-* capabilities.

However, additional standards also increase implementation complexity.

Transport Security vs Message Security

Transport security protects data while it travels between two endpoints.

HTTPS is the most common example.

For example:

Client → Encrypted HTTPS Connection → Server

Message-level security can protect parts of the message itself.

SOAP ecosystems can provide standardized mechanisms for this through WS-Security.

Therefore, organizations with specific enterprise security requirements may consider SOAP.

However, many modern APIs can meet their security requirements using HTTPS and well-designed application-level controls.

Authentication

REST APIs can support several authentication models.

For example:

Client → Access Token → REST API

This approach is common for web and mobile applications.

SOAP services can also authenticate users or systems.

For example, authentication may use enterprise security standards or credentials defined by the service.

Therefore, both approaches can support secure authentication.

Authorization

Authentication determines who is making the request.

Authorization determines what that identity is allowed to do.

For example:

A normal user may read an order.

Meanwhile, an administrator may update or cancel it.

Therefore, authorization is important regardless of whether the API uses REST or SOAP.

The API architecture should enforce permissions on the server side.

Transactions

Some enterprise operations involve several related actions.

For example:

Create Order → Reserve Inventory → Record Payment

If one step fails, the system may need to handle the overall transaction carefully.

SOAP ecosystems include specifications designed for advanced transaction scenarios.

Therefore, SOAP has historically been used in some enterprise environments with formal distributed transaction requirements.

REST applications can also implement transactional business workflows.

However, these are usually handled through application architecture rather than a REST-specific transaction standard.

Reliability

Reliable messaging can be important for enterprise integrations.

For example, a financial or business process may need stronger guarantees around message delivery.

SOAP ecosystems include standards such as WS-ReliableMessaging.

Therefore, SOAP can support standardized enterprise messaging requirements.

REST systems can also build reliable processing using queues, retries, idempotency, and other architectural techniques.

However, those mechanisms are not provided by REST itself.

Idempotency

Idempotency means that repeating the same operation should not create unintended additional effects.

For example, repeating a payment request should not accidentally charge the customer twice.

REST design can use HTTP method semantics and idempotency mechanisms to manage these scenarios.

Meanwhile, SOAP applications can implement similar business safeguards.

Therefore, idempotency should be considered in any API that handles important transactions.

REST for Web Applications

REST is widely used for web applications.

For example:

Web Front End → REST API → Application Server → Database

The front end can request customer, product, or account information through API endpoints.

Therefore, front-end and back-end development can remain separated.

As a result, different interfaces can potentially use the same backend services.

REST for Mobile Apps

Mobile applications frequently communicate with REST APIs.

For example:

Mobile App → REST API → Backend

A banking, delivery, social, or e-commerce app may make many API requests.

Therefore, relatively compact JSON payloads can be useful.

In addition, REST libraries are available across most modern mobile development environments.

REST for SaaS Platforms

SaaS applications commonly expose REST APIs.

For example, customers may want to integrate the SaaS product with:

• CRM
• ERP
• Accounting software
• Marketing tools
• Internal applications

Therefore, a REST API can become an important part of the SaaS product.

In addition, public documentation can make integration easier for external developers.

SOAP for Enterprise Systems

SOAP remains present in many enterprise environments.

For example, organizations may have established integrations between:

• ERP systems
• Financial systems
• Government systems
• Insurance platforms
• Telecom systems
• Legacy enterprise applications

These integrations may already depend on WSDL contracts and SOAP messaging.

Therefore, replacing SOAP simply because REST is newer may not provide enough business value.

SOAP for Legacy Systems

Many long-running enterprise systems expose SOAP services.

Therefore, a modern application may still need to consume SOAP.

For example:

Modern Web Application → Integration Layer → Existing SOAP Service

In this case, rebuilding the existing enterprise service may not be necessary.

Instead, the business can create an integration layer that communicates with it.

REST for Microservices

REST is commonly used between microservices.

For example:

Order Service → Inventory Service

Order Service → Payment Service

Shipping Service → Customer Service

Therefore, services can communicate through clearly defined APIs.

However, REST is not the only option for microservices.

Other communication technologies can also be used depending on performance and messaging requirements.

SOAP and Microservices

SOAP can technically be used in microservice architectures.

However, its additional messaging complexity means it is less common in many modern microservice environments.

Therefore, REST or other lightweight communication approaches are often selected.

However, a microservice may still need to connect with an existing SOAP-based enterprise system.

As a result, mixed architectures are possible.

REST for Public APIs

REST is widely used for APIs offered to external developers.

For example, a company may provide APIs for:

• Products
• Orders
• Customers
• Shipping
• Payments

Developers can work with familiar HTTP methods and JSON.

Therefore, REST can reduce integration friction for many public API use cases.

Clear documentation remains essential.

SOAP for Public APIs

SOAP services can also be exposed externally.

However, they are less common for new developer-focused public APIs.

The XML and WSDL model can create additional integration complexity.

Therefore, businesses often prefer REST when simplicity and broad developer adoption are priorities.

However, existing industries and platforms may continue using SOAP.

REST API Versioning

APIs change over time.

For example, a business may add fields or redesign endpoints.

Therefore, version management is important.

A REST API might use an approach such as:

/api/v1/customers

Later:

/api/v2/customers

Other versioning strategies are also possible.

Therefore, businesses should define an API lifecycle policy before making large APIs publicly available.

SOAP Versioning

SOAP services also need version management.

For example, changing message structures or service contracts can affect existing clients.

Therefore, businesses may publish a new service contract while keeping an older version available.

As a result, versioning remains important regardless of API style.

Documentation

Good documentation is critical for any API.

REST documentation should explain:

• Authentication
• Endpoints
• Parameters
• Request bodies
• Responses
• Errors
• Rate limits
• Examples

SOAP services often provide WSDL definitions.

However, developers may still need additional business documentation.

Therefore, machine-readable specifications do not completely replace human-friendly documentation.

Testing REST APIs

REST APIs can be relatively straightforward to test.

For example, developers can send HTTP requests and inspect JSON responses.

Therefore, both automated and manual testing tools can be used.

Testing should cover:

• Successful requests
• Invalid inputs
• Authentication
• Authorization
• Errors
• Performance

As a result, API reliability can be verified before release.

Testing SOAP APIs

SOAP APIs require testing of structured XML messages and service operations.

For example, tests may verify:

• XML structure
• Service operations
• Authentication
• SOAP Faults
• Contract compliance

Therefore, testing can involve additional protocol-specific details.

However, mature SOAP development tools can automate much of this work.

API Monitoring

Production APIs need monitoring.

For example, teams should track:

• Request volume
• Response times
• Error rates
• Authentication failures
• Service availability

Therefore, monitoring is equally important for REST and SOAP.

In addition, logs should provide enough information to diagnose problems without exposing sensitive data.

Rate Limiting

Public and high-volume APIs may need rate limits.

For example, an API could restrict how many requests a client can make during a certain period.

Therefore, rate limiting can protect infrastructure from excessive traffic.

REST APIs commonly implement these controls through API gateways or application infrastructure.

SOAP services can use similar infrastructure controls.

API Gateway

An API gateway can sit between clients and backend services.

For example:

Client → API Gateway → Backend Services

The gateway may handle:

• Authentication
• Rate limiting
• Routing
• Monitoring
• Logging

Therefore, gateways can simplify API management.

Both REST and SOAP services can be managed through gateway infrastructure, depending on the product and architecture.

REST API Development Cost

REST API development cost depends on complexity.

For example, a simple internal API may require only a small number of endpoints.

Meanwhile, a large SaaS API may require authentication, permissions, documentation, integrations, monitoring, and version management.

Broad planning ranges might look like this:

REST API Project	Approximate Development Cost
Simple REST API	$3,000–$10,000+
Small business API	$5,000–$20,000+
Custom REST API	$15,000–$50,000+
Advanced API platform	$50,000–$150,000+
Enterprise API ecosystem	$100,000–$500,000+

These are broad planning estimates rather than fixed prices.

Therefore, businesses should estimate the project after defining its endpoints, security, integrations, and expected traffic.

SOAP API Development Cost

SOAP projects can involve additional integration and contract requirements.

Broad planning ranges might look like this:

SOAP API Project	Approximate Development Cost
Simple SOAP integration	$5,000–$15,000+
Business system integration	$10,000–$30,000+
Custom enterprise SOAP service	$25,000–$75,000+
Advanced enterprise integration	$75,000–$200,000+
Large integration ecosystem	$150,000–$500,000+

Again, these are broad planning estimates.

Actual costs depend on service contracts, legacy systems, security, data mapping, testing, and integration complexity.

What Affects API Development Cost?

Several factors can affect the cost of either approach.

For example:

• Number of endpoints or operations
• Business logic
• Authentication
• Authorization
• Database integration
• Third-party integrations
• Data transformation
• Documentation
• Testing
• Monitoring
• Traffic volume

In addition, integration with poorly documented legacy systems can increase development time.

Therefore, technical discovery is important before estimating a complex API project.

REST API Advantages

REST provides several practical benefits.

Simpler Development

Developers can work with familiar HTTP concepts.

Therefore, development can be relatively straightforward.

Lightweight Payloads

JSON can reduce message size compared with verbose XML structures.

As a result, REST works well for many web and mobile applications.

Flexible Data Formats

REST does not require XML.

Therefore, APIs can use JSON and other formats when appropriate.

Web-Friendly Architecture

REST works naturally with HTTP methods, URLs, caching, and status codes.

As a result, it fits modern web infrastructure well.

Broad Developer Adoption

REST is widely understood across development ecosystems.

Therefore, finding libraries, documentation, and developers is usually straightforward.

REST API Limitations

REST also has limitations.

No Single Built-In Security Standard

REST does not define one complete security framework.

Therefore, teams need to choose and implement appropriate security mechanisms.

No Built-In Distributed Transaction Standard

Complex transactions need application-level architecture.

As a result, developers need to design these workflows carefully.

API Designs Can Become Inconsistent

REST provides flexibility.

However, different teams may design endpoints differently.

Therefore, API design standards are important.

Documentation Is Essential

An undocumented REST API can be difficult to integrate.

Therefore, teams should maintain clear and current specifications.

SOAP API Advantages

SOAP provides different strengths.

Formal Service Contracts

WSDL can define operations and data structures clearly.

Therefore, integrations can follow a strict contract.

Standardized Messaging

SOAP messages follow defined XML structures.

As a result, communication can be highly standardized.

Enterprise Security Standards

WS-Security can support specific message-security requirements.

Therefore, SOAP can fit some enterprise environments well.

Reliability Standards

SOAP ecosystems provide specifications for reliable messaging.

As a result, organizations with these specific requirements can use standardized approaches.

Mature Enterprise Support

Many established enterprise systems already support SOAP.

Therefore, SOAP can remain practical when integrating with existing infrastructure.

SOAP API Limitations

SOAP also has disadvantages.

Greater Complexity

XML, WSDL, and additional standards can increase development complexity.

Therefore, developers may require more specialized knowledge.

Larger Messages

SOAP XML can be verbose.

As a result, network and processing overhead may be higher.

Less Convenient for Modern Front Ends

Web and mobile developers commonly prefer JSON-based APIs.

Therefore, SOAP can create additional work for these applications.

More Rigid Structure

Strict contracts can provide consistency.

However, they can also make changes more complicated.

Therefore, version management requires careful planning.

When Should You Choose REST?

REST may be appropriate when:

• You are building a web application
• You are developing a mobile app
• You need a public developer API
• JSON is the preferred data format
• You are building a SaaS product
• You need relatively lightweight communication
• Your architecture uses web-oriented services
• Simple integration is important

Therefore, REST is a common choice for new application APIs.

However, requirements should still determine the final architecture.

When Should You Choose SOAP?

SOAP may be appropriate when:

• An existing enterprise system requires SOAP
• WSDL contracts are already established
• Specific WS-* standards are required
• You are maintaining legacy enterprise integrations
• Message-level security requirements match SOAP standards
• Formal messaging contracts are a major requirement

Therefore, SOAP can remain a practical choice for specific enterprise environments.

However, businesses should not choose it solely because it has more formal specifications.

Can REST and SOAP Work Together?

Yes.

A business can use both within the same technology environment.

For example:

Mobile App → REST API → Integration Service → SOAP Enterprise System

The mobile application communicates through REST.

Meanwhile, the integration service communicates with the existing SOAP system.

Therefore, businesses can modernize customer-facing applications without immediately replacing every legacy integration.

Migrating from SOAP to REST

Some businesses consider replacing existing SOAP services with REST APIs.

A migration might look like:

Existing SOAP Service

↓

Business Logic Review

↓

REST API Design

↓

Testing

↓

Client Migration

However, migration should have a clear business reason.

For example, REST may make sense when the organization needs easier mobile or third-party integration.

On the other hand, a stable internal SOAP integration may not need replacement.

Therefore, modernization should focus on business value rather than technology trends alone.

REST vs SOAP for Small Businesses

Small businesses often need straightforward integrations.

For example:

Website → CRM

or:

Mobile App → Backend

Therefore, REST is commonly suitable because many modern services already provide REST APIs.

In addition, development can be relatively simple.

However, a small business may still need SOAP when integrating with an external enterprise system that requires it.

REST vs SOAP for Growing Businesses

Growing companies often integrate more applications.

For example:

CRM + ERP + Website + Mobile App + Customer Portal

REST APIs can provide a flexible integration layer.

Therefore, new applications can access business services through consistent interfaces.

However, some ERP or industry-specific systems may still expose SOAP services.

As a result, growing businesses may use both.

REST vs SOAP for Enterprises

Enterprises often have mixed technology environments.

For example, newer applications may expose REST APIs.

Meanwhile, older systems may continue using SOAP.

Therefore, an enterprise architecture might look like:

Web + Mobile → REST APIs

Integration Layer

ERP + Legacy Systems → SOAP Services

As a result, REST and SOAP can coexist for many years.

The goal should be reliable integration rather than forcing every system to use the same technology.

Common REST API Mistakes

REST APIs can become difficult to maintain when design standards are ignored.

For example, common mistakes include:

• Inconsistent endpoint names
• Incorrect HTTP methods
• Poor error responses
• Weak authentication
• Missing authorization
• No versioning strategy
• Poor documentation
• Returning unnecessary data

Therefore, REST’s flexibility needs disciplined API design.

Common SOAP API Mistakes

SOAP integrations can also fail because of poor implementation.

For example:

• Incorrect XML structures
• Contract mismatches
• Poor error handling
• Security misconfiguration
• Unnecessary complexity
• Weak documentation

Therefore, using a formal protocol does not automatically guarantee a reliable integration.

Good architecture and testing remain essential.

Questions to Ask Before Choosing

Before choosing REST or SOAP, consider:

• What systems need to communicate?
• Is this a new API or an existing integration?
• Who will consume the API?
• Is it for web or mobile applications?
• Does an existing system require SOAP?
• Is JSON preferred?
• Do we need a formal WSDL contract?
• Are specific WS-* standards required?
• What security requirements apply?
• How much traffic will the API receive?
• Do we need caching?
• What are the performance requirements?
• How will errors be handled?
• How will the API be versioned?
• Who will maintain the API?
• What is the development budget?

Therefore, architecture should follow business and technical requirements rather than popularity alone.

Frequently Asked Questions

What is the main difference between REST and SOAP?

REST is an architectural style commonly used to build web APIs.

SOAP, in contrast, is a standardized messaging protocol based on XML.

Therefore, REST generally provides more flexibility while SOAP provides a stricter messaging structure.

What does REST stand for?

REST stands for Representational State Transfer.

It describes architectural principles for designing networked applications.

What does SOAP stand for?

SOAP stands for Simple Object Access Protocol.

It defines a standardized format for exchanging structured messages.

Does REST only use JSON?

No.

REST does not require JSON.

However, JSON is widely used because it is lightweight and convenient for web and mobile applications.

Does SOAP only use XML?

SOAP messages use XML.

Therefore, XML is a core part of the SOAP messaging standard.

Is REST faster than SOAP?

REST can have lower message overhead, especially when it uses compact JSON payloads.

However, overall API performance also depends on infrastructure, databases, application logic, caching, and network conditions.

Therefore, REST is not automatically faster in every situation.

Is REST more secure than SOAP?

Neither is automatically more secure.

REST commonly relies on HTTPS and application-level authentication and authorization.

Meanwhile, SOAP can also use HTTPS and may use standards such as WS-Security.

Therefore, security depends on requirements and implementation.

Is SOAP outdated?

No.

SOAP is less common for many new public and mobile APIs. However, it remains in use across enterprise and legacy integrations.

Therefore, businesses may continue using SOAP where it meets existing requirements.

Can REST replace SOAP?

Sometimes.

A new REST API can replace or wrap an existing SOAP service when there is a clear reason to modernize the integration.

However, stable SOAP systems do not always need replacement.

Can an application use both REST and SOAP?

Yes.

For example, a mobile application may communicate with a REST backend while that backend integrates with an existing enterprise SOAP service.

Therefore, mixed architectures are common.

Final Thoughts

REST and SOAP both allow software systems to exchange information.

However, they take different approaches.

REST is an architectural style that works naturally with modern web technologies.

For example, REST commonly uses:

• HTTP
• Resource-based URLs
• Standard HTTP methods
• JSON
• HTTP status codes

Therefore, REST is widely used for web applications, mobile apps, SaaS platforms, and public APIs.

SOAP, in contrast, is a formal messaging protocol.

For example, SOAP provides:

• XML-based messages
• Structured envelopes
• WSDL service contracts
• SOAP Faults
• Enterprise WS-* specifications

As a result, SOAP remains relevant for certain enterprise and legacy integrations.

However, the decision does not need to be based on which technology is newer.

Instead, businesses should consider their integration requirements.

For a new mobile, web, or SaaS application, a REST-style API may align naturally with the surrounding technology.

Meanwhile, an organization integrating with an established enterprise service may need SOAP because that is the interface the system already provides.

In addition, some organizations can benefit from using both.

In simple terms:

REST API = Flexible, web-friendly, and commonly used for modern applications.

SOAP API = Structured, standardized, and still important for specific enterprise integrations.

Ultimately, businesses should ask:

“Do we need a flexible web-oriented API, or do our integration requirements depend on SOAP’s formal messaging and enterprise standards?”