The growth of the API Market in the US continues to climb year over year, with an expected increase of 34% - totaling a projected $7.5B market size in 2026.

From massive global corporations to local businesses, the widespread use of APIs has permanently changed the face of all major industries.

With REST APIs being the most commonly used APIs on the Web, it’s essential to understand what separates them from other types of APIs.

In this article, you will learn everything you need to know about REST APIs to better understand how you can leverage their potential to reach your goals.

What Is a REST API?

A REST API is a standardized approach to building APIs that entails using the representational state transfer (REST) architectural style to communicate with servers.

Designed in 2000, it’s been widely recognized as the go-to API development framework for creating web applications, SaaS products, and other web-based software products.

REST APIs can be built with almost any programming language and support different data formats.

For an API to be deemed as REST, it has to meet the following seven architectural constraints outlined in the original dissertation written by the creator of REST. Roy Fielding:

1. Null style: the term refers to the architecture style where you start with no constraints and then start layering constraints on top of each other in a controlled and logical way.
2. Client-server: In REST APIs, the client and server are completely separated and can’t interact with one another in any other way except through an API, allowing them to evolve independently.
3. Uniform interface: Regardless of where API requests may come from, all of them should be identical when they try to gain access to the same resource.
4. Statelessness: All API calls must contain all the information needed for processing a request without any stored context on the server.
5. Cache: If applicable, reusable resources should be stored on the client or server to optimize the performance, making REST APIs a scalable solution.
6. Layered System: A REST API is a system composed of multiple layers, each of which has a single purpose. One of the most common examples is a three-tier system made up of three layers: data access, business logic, and presentation.
7. Code on Demand: REST APIs make it possible to dramatically extend their functionality by allowing them to send executable code - that should only run on-demand.

How Does a REST API Work?

In this section, we will take a deep dive into how REST APIs work from within. To start with, we are going to break down how a REST API fits into the client/server ecosystem for you to see the big picture:

1. The user sends an API request through the client (the app or the frontend part).
2. The API processes the request and queries the database (the backend part) to execute it on the backend side.
3. The API sends a response to the client when the request has been executed.

This is the natural order of things when it comes to any APIs.

In order to communicate, REST APIs use all possible CRUD (create, read, update, delete) operations, the industry-standard HTTP verbs, that describe the things you want to do when interacting with your client and server.

In REST APIs, HTTP methods, the equivalent of CRUD, are used to communicate both with the client and the server:

CRUD OperationHTTP MethodCreatePOSTReadGETUpdatePUTDeleteDELETE

Additionally, you can use the PATCH method to update your data partially.

When it comes to API requests, it contains multiple building blocks:

• The Operation: the HTTP method that is being applied.
• The Endpoint is the point of entry in a communication channel when two systems interact, allowing the API to perform a specific task.
• The Body: this API term characterizes the data that you want to send in the API request.
• The Headers: a particular part of a REST API request which contains the meta-data related to the request - be it an API key or authentication data.

The response is typically processed and stored in JSON or XML formats to deliver it back to the client. Other formats may include XLT, HTML, PHP, Python, or a simple text string.

The Pros and Cons of REST APIs

The flexible design principles of REST helped this type of API quickly become the most widely used framework today.

To help you make an informed decision, in this section, we will cover the unique benefits and challenges of using REST APIs for your development project:

• Simplicity: REST APIs are relatively easy to master for any developer if you compare them to SOAP or other competitors, significantly shortening the learning curve and promoting ease of use.
• Standardization & Uniformity: Thanks to the uniform way of communication, you don’t need to worry about the format of your data and requests each time.
• High Scalability: As your service grows, you can easily modify the architecture without major structural overhauls.
• Statelessness: The fact that REST APIs are stateless means that you don’t have to worry about data state or track that across the client and server.
• High Performance: Thanks to the fact that REST APIs support caching, this preserves a significant amount of resources, ensuring high performance even as the service gets more sophisticated over time.

However, the very same principles that result in an extensive range of benefits bring with them a few drawbacks that you need to consider during the development process:

• Negligible Latency: REST APIs are a great way to run your web service. However, you need to consider that some of the architectural constraints may lead to higher latency if left unaddressed.
  As an example, since RESTful APIs are based on the layered system, the more layers you stack on top of each other - be it for caching or load balancing purposes - the more latency these layers have.

• Higher Bandwidth Usage: High performance at scale can come at the cost of higher bandwidth usage if developers fail to optimize your API correctly.

For instance, the stateless nature of REST APIs may lead to the client sending responses with redundant information, leading to higher resource consumption.

• REST API Versioning: APIs are regularly versioned to sidestep any potential compatibility issues.

When that happens, multiple endpoints can remain active, effectively resulting in multiple APIs being used simultaneously.

However, the biggest challenge is not resource consumption or versioning - it’s making your REST API safe for your users.

Why Security Is the Biggest Concern for REST APIs

According to a report from IBM Security X-Force, two-thirds of cloud breaches can be attributed to misconfigured APIs.

A long list of recent API security incidents shows that APIs are increasingly targeted for data theft due to security gaps like weak authentication or business logic errors.

While tech companies were the most frequent target of successful API breaches (58 percent), regulated organizations and industries were frequent targets as well: government (10 percent), healthcare (4.5 percent), financial (6 percent), and telcos (3 percent) were common successful targets of data breach attacks.

Given the frequency of these breaches and that REST APIs dominate the scene across all major industries, companies need to be aware of what poses the biggest risks and how to mitigate them.

REST API Security: Best Practices

There are a myriad of ways to break into your API and cause significant damage to your company.

The average cost of a data breach is estimated to be $8.64 million for US-based companies.

Considering that 83 percent of consumers will stop the relationship with a company that became a victim of a successful cyberattack, securing API has never been more critical.

To help you get started, these are the essentials that should help you protect your API against simple cyberattacks:

• Always use HTTPS: You should always use SSL to ensure higher security standards.
• Use password hashing: Password hashes add another layer of security, protecting the integrity of sensitive data even if a password was compromised.
• Avoid exposing sensitive data in URL strings: Any data that hackers can potentially use to break into your system, from usernames to session tokens, must not be included in the URL string.
• Implement OAuth: OAuth is a widely recognized authorization framework allowing data exchange without exposing sensitive information.

However, since the techniques and methods used by hackers have constantly been evolving, continuous, comprehensive, and automated API testing is how some of the world’s largest companies keep their APIs safe.

Meet Your Reliable API Testing Partner

APIsec provides an enterprise-grade, automated, continuous API security platform that instantly detects top vulnerabilities, including the OWASP Top 10, business-logic, role-configuration, and access-control flaws, otherwise impossible to find using manual security tests.

The platform executes a strict assessment of your REST API and targets your API vulnerabilities that security attackers can use to steal sensitive data - all for a fraction of the cost of professional manual penetration testing.

If you’re looking for a way to keep your API safe from hackers by leveraging cutting-edge technology, reach out to us today to get a free penetration test of your API.