API Security

Differences SOAP vs REST API

Differences SOAP vs REST API

SOAP and REST are two of the most used terms in the API development sector. If you don’t have thorough knowledge of the two, you may wonder:

  • Why should a developer choose and ditch others? 
  • Can these two be used at a time?
  • …and so on.

Well, it’s a lot of information and is covered bit by bit in this post. So, if you have anything to do with API development and API security and are willing to bring SOAP or REST at work, this post is just the right thing to refer to before starting off.

Learning Objectives

What Is SOAP?

Let’s begin with knowing the fundamentals of SOAP. SOAP means Simple Object Access Protocol and is an API development protocol designed with a motive to bring stability and consistency in the data exchange process, which happened between programs built using different programming languages, tools, and platforms. 

It presents a globally recognized set of rules and regulations that anyone willing to achieve seamless client and server interaction needs to follow. Requests in SOAP are delivered using envelopes. These envelopes hold information crucial for request processing. Mostly, the key parts of the SOAP envelope are a header and body attributes. 

Basic Features of SOAP 

Here are some of the key features of SOAP that make it stand out:

  • It is built with XML and can only be used for web services. 
  • SOAP uses a lot of bandwidth for message processing as SOAP messages hold a huge chunk of data. 
  • SOAP can’t be used by REST 

When To Use SOAP?

As SOAP plays a key role in API development, here are the areas where its implementation will be proved fruitful.

  1. Use it for synchronous processing and invocation subsequently 

If the client needs to have certain application reliability and enhance API security then the latest SOAP standard, SOAP 1.2, is here to here. It offers a couple of professional features for seamless and synchronous processing.  

It also supports subsequent invocation of certain APIs and incorporates needed security practices. 

  1. Use it as an official communication 

In situations when server and client are already ready to exchange data in a format then use SOAP 1.2 as it offers a wide range of rigid specifications for such a communication. 

  1. Use it for seamless processing of stateful operations 

For an application that has an obligation to maintain the state from one request to another, using SOAP 1.2 will make the job quick and easy as it endows the developers with a recognized WS* structure for such tasks. 


Example SOAP API 

<?xml version="1.0"?>
<m:Trans xmlns:m="https://www.example.com/transaction/"
  <m:GetEmployee xmlns:m="https://www.example.com/prices">

Pros and Cons Of SOAP 

Now that the basics of SOAP are clear, it’s time to learn about the merits and demerits that a developer will enjoy with SOAP. 


  • With SOAP, developers will be able to use WSDL. WSDL is the Web Services Description Language used widely to explain web service procedures and access methods. It serves as a comprehensive resource to learn about API consumption. It makes API development a seamless experience. 
  • SOAP is a great tool to have when working with multiple extensions is the aim. It has an amazing compatibility extension like WS Addressing, WS Security, and WS Federation and can join hands with them to double-up the application capabilities. In short, it makes creating highly functional apps a little strenuous task. 
  • SOAP is a protocol-neutral protocol and can be accessed easily via HTTP, SMTP, TCP, and many other kinds of application protocols. This also means a wide range of users can bring it into practice.  


  • While SOAP is doing a wonderful job, it lacks at certain fronts. And, before you think of using it, knowing the areas wherein can disappoint you is crucial. 
  • The biggest drawback of SOAP is that it uses XML for payload data transfer. XML takes longer than usual time for this job that further gives birth to multiple performance issues. 
  • The second thing that can force people to stay away from SOAP is its complicated syntax. It can only work with XML and it demands a little more effort and time to extract or read data from envelopes. So, it lengthens the API development time.  

What Is REST?

REST or Representational State Transfer is an undividedly different approach. It’s a type of architectural pattern employed widely for the modern web-based application development task. It administers the key application components like files, even objects, and media components.  

APIs, produced using REST, is ready to present website or application functionality over the HTTP and are supportive with HTTP verbs like getting and POST 

As REST APIs have unmatched interoperability on the web, they have become the prime choice of many. 

REST protocol

Basic features of REST  

  • REST takes the help of Uniform Service locators to reach at the heart of the hardware device components. 
  • REST is the base for data communication, which happened in the modern application infrastructure.
  • While SOAP can’t use REST, REST can use SOAP. It uses it as a key protocol of web services describing the tool. In fact, it will need SOAP for completing the application development as it’s only an architectural pattern and doesn’t have any standard format for explaining web services.  

When to use REST?

If one wants to utilize the full potential of REST, using it in the right place is the key. Here are the key areas wherein it can do wonders. 

  1. Use it when you have restricted bandwidth 

As specified above, SOAP messages utilize a lot of bandwidth. So, if there is a crisis of resources and bandwidth then REST is a life savior. It works wonderfully even if network bandwidth is restrained. 

  1. Use it when there is no need to maintain a state

Operations that involve no adherence with the statelessness in transferring information from one request to another can be done with full accuracy with REST. 

  1. Use it when catching a lot of requests is the need of the hour

Caching of requests is a key operation and needs to be accomplished with full accuracy. With REST, it’s easy to catch the information as it supports it by all means. In fact, it has handled catching information of the same request multiple times. By doing so, it cuts down the time invested in application development. 

  1. Use it when easy coding is required

The coding of REST APIs and services is far more seamless than SOAP. If there is a time crunch and a quick yet effective web application service is required then REST is the right choice to make.  

Example REST API

An example REST API object is shown here:

"name": "XYZ",
"location": "India",
"title": “developer”,
joinYear: 2010

Pros and Cons Of REST


  • REST came into being a little later than SOAP. Yet, it has managed to garner a notable significance all because of the impressive benefits it renders to the end-users. Here are the perks that every REST user will enjoy.
  • REST is a stateless pattern and allows each web service call to carry all the necessary information. It doesn’t bank upon any other client-server context for information storing. Because of this, it speeds up the entire process. 
  • APIs developed using REST are highly flexible and can collect the server data in multiple formats. Formats like Atom, JSON, and XML are well supported with REST. So, great freedom in using the format is granted. 
  • In REST, responses are catchable. Such responses are great to improve the web service performance as all the unwanted calls to the backend are removed. 


  • No matter how lucrative REST seems, it has some downsides as well. For instance, there are no specific and globally recognized standards, which is the case with SOAP. Because of this, developers end up using it as per their choices and API development becomes complex. 
  • There are a couple of REST permutations. 
  • REST-based applications are also very cramped to the HTTP protocol which restricts them.  

REST API Security Vulnerabilities

  • Injection Attacks

Most common and quite dangerous among others, these intrusions involve insertion of malicious code to a protected API or application. If ignored, it could have severe outcomes, including illicit grant to threat actors into the main system/app, inserting invalid input to the RESTAPIs, and various other threats. Its common-most variants are XSS and SQLi.

APIs that are not backed with best authentication practices like OAuth and API keys are prone to this API cyber risk. It refers to bypassing the methods of identity/authority verification and taking admin-like control over APIs in question.

When at rest and in use APIs are not properly encrypted, they become the victim of this attack. The lack of military-grade encryption opens the door to opportunities for threat actors and they steal/manipulate/misuse sensitive information like bank details, personal details, etc.

When adequate access control measures aren’t implemented correctly, APIs are easy to break down. Depending upon the intent and purposes of the hacker, threats like unauthorized access to multiple accounts, unverified exchange of data/info, and many more hassles are created.

  • HTTP and Lack of TLS

APIs, lacking TLS and HTTP quality standards, is nothing but an open invitation to hackers. The lack of TLS encryption creates an ideal situation for an MITM attack.

MiTM or Man-in-the-middle, whatever you call it; this safety vulnerability allows a threat actor to be a part of secured and sensitive communication happening through the APIs and misuse it.

  • Parameter Tampering

With an intent to alter crucial parameters like price and permission for personal gains, this attack involves modifying the information being exchanged through the compromised channel.

Protect Your REST APIs

SOAP API Security Vulnerabilities

  • DoS Attack

A very common cybersecurity threat for the APIs, DoS stands for Denial of Service and refers to bombarding numerous API calls to make a specific API unavailable for use.

Often referred to as SOAP injection, XXE is the scenario wherein insecure user input is transferred to server-side SOAP messages and XML documents. Using the XML metacharacters, attackers can alter the pre-created XML and conduct such an illicit activity.

It is what an attacker uses to modify the application-generated database queries and make them work as per his will. When performed at SOAP API, it refers to introducing corrupted SQL queries to the API calls.

  • XAML Injections

It implicates the insertion of malicious codes in the XAML, a mark-up language.

This attack takes place when a vulnerable user-side input is transferred to the SOAP API. When it happens, attackers have the full control over the comprised API with anything that they want.

  • SOAPAction Spoofing

SOAP Action Spoofing or MiTM attack concerns introducing an attacker in the middle of the server-client connection for eavesdropping, data stealing, or other purposes.

  • Broken Access & Authorization

Caused due to the absence of acceptable access/authorization validation criteria, this type of API security threat can lead to hassles like modified URLs, JSON Web Token tempering, and many more.

XSS implies communication compromise by an API. The 2 communicating entities here are the server and vulnerable API.

Why is REST Faster Than SOAP Web Services?

As quoted above, SOAP uses a complex and standard format. There is no shortcut. Everything has to follow certain rules and regulations. XML is already very tedious. Hence, it is time-consuming. 

REST, on the other hand, uses a simple route, JSON, and even cuts down the communication time by caching the information. So, it reaches its target at a much faster pace. 

protocol layering

SOAP vs REST API: Which is More Secure? 

API security is one aspect that would be the priority, regardless of what approach you chose. While REST is faster than SOAP and makes things easier, we have to admit that SOAP is more secure.  

Both SOAP and REST can use SSL or Secured Socket Layer for protecting the data during the API call request. However, SOAP goes an extra mile and supports Web Services Security as well. Using this extension, application developers can double-up the API security and keep tons of hassles at bay. So, SOAP is better than REST when API security is a matter of concern.  


Benefits of REST Over SOAP 

  1. REST grants a wide range of data formats to work with. SOAP is very limited at this front. Other than XML, it doesn’t support anything else. 
  2. REST, when used with JSON, is a piece of cake. Without much complexity, it can be used.  
  3. Brower clients, using REST, are going to enjoy great technical support.  
  4. As caching of information, done is REST, is not altered, and is dynamic, the applications will have better performance. 
  5. It’s most commonly used and has been praised by leaders like Amazon, eBay, Google, and Yahoo for its seamless operations. 
  6. REST is easy to work with at every front. Whether you talk about its ability to work with less bandwidth or amazing integration power, it stands out at every front. Developers will be able to work from scratch and finish the job in less time. However, that speediness will have no negative impact on the functionality. It will still be top-notch. 


Benefits of SOAP Over REST 

  1. SOAP offers a pre-made retry logic that is used as compensation for failed communication. REST has no such thing. In case of communication failure, retrying is the only option. 
  2. SOAP is a highly standardized format and suggests a certain set of rules. Because of this, maintaining quality and standardization becomes easy. REST has no standard rules. 
  3. The standard HTTP protocol of SOAP makes it possible to remain functional across multiple firewalls and proxies without getting involved in tedious modification. 
  4. When it comes to compatibility with extensions, SOAP has an upper hand as it can work wonderfully with WS-Addressing, WS-ReliableMessaging, WS-Coordination, and various other options, as suggested by W3C. 

API arhitectural styles

Organized in terms ofenveloped message structurecompliance with six arhitectural constraints
FormatXML onlyXML, JSON, HTML, plain text
Learning curveDifficultEasy
Use casesPayment gateways, identity managment CRM solution financial and telecommunication services, legacy system supportPublic APIs simple resource-driven apps


SOAP and REST; both are the two most used and acceptable API development approaches. While SOAP makes everything highly standardized. 

REST is easy to work with. So, it’s hard to pick one. It entirely depends upon the organization and its needs. Keep your facts straight, figure out what you want, and then make a choice. Either way, there are some losses and some gains. Just weigh them down intelligently and pick what your mind says.

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