REST API vs API: What’s the difference?

What is the difference between a traditional API and a REST API? To answer this question, let's take a quick look at how it all started.

Back in 2000, emerging startups like Salesforce, Amazon, and eBay set out to change the way we did business on the web by adding the ".com" and making products and services available to customers through a single website.

When you hear the acronym API, it almost always refers to the modern approach of using HTTP to provide access to machine-readable data in a JSON or XML format, often referred to simply as Web APIs.

This article focuses on the REST API, defining it and analyzing how it differs from other APIs.

What is API and REST API?

An API, or Application Programming Interface, is a set of protocols that allow different software components to transfer data. Developers use APIs to bridge the gaps between small, discrete pieces of code to create robust, stable, secure, and responsive applications.

There are many different types of APIs and ways to categorize them, for instance, by who has access to them or by their architectural style. We're going to focus on the most common architectural styles, which include the following:

• REST is the most popular API architecture for data transfer. In a RESTful context, resources (which are like entities in a database) are accessed through endpoints, and operations are performed using standard HTTP methods such as GET, POST, PUT, and DELETE.‍
• SOAP, or Simple Object Access Protocol, uses XML to pass highly structured messages between a client and a server. SOAP is often used in enterprise environments or legacy systems, and while it includes advanced security features, it can be slower than other API architectures.‍
• GraphQL is an open-source query language that allows clients to interact with a single API endpoint to retrieve the exact data they need without chaining multiple requests. This approach reduces the number of round trips between a client and a server, which is useful for applications running on slow or unreliable network connections.
• ‍Webhooks are used to implement event-driven architectures where requests are automatically sent in response to event-based triggers. When a specific event occurs in an application, such as a payment being made, the application can send an HTTP request to a pre-configured Webhook URL with the relevant event data in the request payload. The system receiving the webhook can then process the event and take the appropriate action.
• ‍gRPC, or Remote Procedure Call, APIs were created by Google. In gRPC architectures, a client can call a server as if it were a local object, making it easier for distributed applications and systems to communicate with each other.

What is REST API?

REpresentational State Transfer, or REST, is a software architectural style that developers apply to web APIs. REST APIs provide simple, uniform interfaces because they can be used to make data, content, algorithms, media, and other digital resources available through web URLs. In essence, REST APIs are the most common APIs used on the Web today.

The key elements of a REST API are:

• a client or software that runs on a user’s computer or smartphone and initiates communication
• a server that offers an API as a means of accessing its data or functionality
• a resource, which is any piece of content that the server can provide to the client

To get access to a resource, the client sends an HTTP request. In return, the server generates an HTTP response with encoded data on the resource. Both types of REST messages are self-descriptive, meaning they contain information on how to interpret and process them.

Key differences between REST API and API

While APIs and REST APIs are often used interchangeably, there are some important differences between the two. APIs can refer to any type of interface that enables communication between different systems. REST APIs are a specific type of API that adheres to the constraints of the REST architecture. 

RESTful APIs use HTTP requests to interact with data, while traditional APIs can use a variety of protocols. Also, RESTful APIs are designed to be stateless, meaning that each request contains all the information necessary to complete it, whereas traditional APIs may require additional context or information to be passed between systems.

This particular type of API adheres to six specific architectural imperatives:

• Completely stateless: Requests from the client to the server must contain all the information necessary for the server to understand and process them appropriately. The server can't have any information about the client's state.
• Native caching: Data within a response to a request must be marked as cacheable or non-cacheable.‍
• Uniform interface: To have a uniform interface, several architectural constraints are required to guide the behavior of components. Resources should be unique so that they can be identified by a single URL.
• ‍Code on demand: Because REST APIs download and execute code in the form of applets or scripts, there's more functionality available to the client. Often, a server will return a static representation of resources in the form of XML or JSON. Servers can also send executable code to the client if necessary.
• ‍Client-server architecture: The uniform interface separates user concerns from data storage concerns. The client domain is concerned with UI and request gathering, while the server domain focuses on data access, workload management, and security. The separation of client and server allows each to be developed and enhanced independently.‍
• Layered system: REST allows for an architecture composed of hierarchical layers. Each component cannot see beyond the immediate layer with which it interacts.

Comparison of key features

Security

Although RESTful APIs provide an easier way to access and manipulate applications, security issues can still arise. For example, a client can send thousands of requests per second and crash your server. Other security challenges with REST APIs include:

• Lack of proper authentication
• Lack of rate limiting and throttling
• Lack of payload encryption
• Incorrect implementation of HTTPS
• Weak API keys that are easily compromised

Scalability

REST APIs are highly scalable. They are stateless, meaning that each request contains all the necessary information for the server to process it. This design allows REST APIs to handle a large number of concurrent requests and scale easily across multiple servers.

Speed

The speed of data transfer and the impact on data transfer speed can vary depending on the type of API involved.

Here are a few things to keep in mind:

• Synchronous APIs require the sender to wait for a response from the receiver before proceeding with other tasks. In this case, the data transfer speed depends on the response time of the receiving system. If the receiving system takes a long time to process and respond to the request, it can slow down the overall data transfer speed.
• Asynchronous APIs allow the sender to continue with other tasks without waiting for a response from the receiver. The sender sends the data and receives an acknowledgment that the data has been received, but the processing or response from the receiver occurs independently. As a result, the data transfer speed can be faster compared to synchronous APIs because the sender can immediately move on to other tasks.
• The speed of data transfer in RESTful APIs can be affected by factors such as network latency, server response time, and the size of the data being transferred. Larger data payloads or slow server response times can slow the overall transfer speed.
• WebSockets provide a persistent, bi-directional communication channel between a client and a server. Unlike traditional HTTP requests, which are stateless, WebSockets maintain a persistent connection, enabling real-time data transfer. WebSockets are designed for low-latency, high-throughput data transfer, making them ideal for applications that require real-time updates. Compared to RESTful APIs, WebSockets can achieve faster data transfer speeds due to their persistent connection and reduced overhead.
• GraphQL is a query language and API runtime that provides a great approach to data retrieval. With GraphQL, the client can specify exactly what data it needs, reducing over-fetching and under-fetching of data. This selective data retrieval can optimize data transfer speed by minimizing the amount of unnecessary data transferred over the network.

Choosing the right API for your needs

Whether selecting an existing API for use in a software project or building a new API from scratch, consider the following:

• Clear documentation. APIs are software, and like any software, they require comprehensive documentation that provides developers with how-to guidance, reference usage, and sample use cases to help developers apply the API quickly and successfully.‍
• Ease of adoption. Keep the API simple, provide an easy way to acquire the API-such as downloads and account sign-up-and ensure solid API support that can answer any developer questions. Otherwise, the API will be too inconvenient to integrate, and developers will bypass it in favor of other APIs that are easier to adopt.‍
• Ease of use. A good API is simply easy to use, with intuitive call structures. Even the most powerful API will be ignored if it uses cumbersome calls and responses. Simplicity, consistency, clarity, and backward compatibility - with clear deprecation - are hallmarks of a good API.
• ‍Stability and reliability. Good APIs are developed like any other software, which should include extensive testing for bugs and clear metrics for performance, such as how many client-server calls per second the API can handle and other relevant factors. Buggy APIs with inconsistent performance will be quickly abandoned by developers. APIs used through third-party vendors must be highly available.
• ‍Security. APIs must support security through strong authentication - where only authorized users can use the API. In addition, any data exchanged over the API should be encrypted or otherwise protected from theft.

Considerations for project type and industry

Well, every project and industry is different in terms of goals and requirements. Just keep the following considerations in mind:

For projects:

• Understand your project requirements and goals. Consider the specific functionality, data, or services you need to access through an API. Determine the types of operations like data retrieval, data manipulation, authentication, or integration with third-party services.

• Consider project type. Different project types may have varying API requirements. For instance, web developers are usually looking for APIs that provide web services, such as RESTful APIs or GraphQL APIs, while mobile app developers are looking for APIs that offer mobile-specific functionalities like push notifications, location services, user management, or in-app purchases.

For industry:

• Evaluate security and compliance. Depending on your industry, you may need to prioritize APIs that offer robust security measures and comply with relevant regulations (e.g., GDPR, HIPAA). Look for APIs that support authentication mechanisms like OAuth, API keys, or tokens. Consider whether encryption, privacy, or compliance certifications are required.
• ‍Check integration capabilities. Consider the existing technologies, frameworks, or platforms used in your industry. Make sure that the API you choose can be easily integrated. Look for client libraries, SDKs (Software Development Kits), or code samples provided by the API provider that support your preferred programming languages or frameworks.

One of the great things about APIs is that you can test and experiment with them on a small scale or in a sandbox environment before committing to them fully. Experiment with sample requests, evaluate the API's response times, security, reliability, and overall performance, and determine whether the API meets the performance expectations and provides the functionality you need.

Directual has everything you need to build your own APIs. Our API builder can help you configure complex API settings, such as filtering, validating, sorting, custom query parameters processing, and (a unique Directual feature!) calling synchronic scenarios. Check out our 101 crash course to start building REST APIs tailerod to your needs like a pro.

Pros and cons of REST APIs and traditional APIs

REST

💪 Pros

With REST APIs, operations are performed using a variety of HTTP methods, including GET, POST, PUT, DELETE, OPTIONS, and PATCH. This makes REST APIs extremely powerful.

The client and server are completely decoupled, allowing for layers of abstraction that help maintain flexibility as a system grows and evolves. In addition, REST is cache-friendly and supports multiple formats, which is important when you're building public APIs. Flexible data formatting makes REST APIs extremely useful for a wide variety of applications.

REST APIs are most often used as management APIs to interact with objects in a system, making them useful for building simple resource-driven applications that don't require a lot of query flexibility.

😩 Cons

REST APIs metadata creates large payloads that can sometimes cause more problems. You can get over- and under-fetching problems that require more API requests, slowing down the process.

There is no required structure for messages. As a result, there is a lot of tinkering when it comes to implementation - which can lead to unnecessary frustration and bottlenecks.

SOAP

💪 Pros

SOAP is completely independent in terms of programming language and processing platform. The standardized format ensures that no matter what is receiving the message on the other end, the request can be executed.

This type of API also helps developers resolve issues before they become critical because native error handling is already in place.

One of SOAP's greatest strengths is its ability to provide secure data transfer in situations where two parties have agreed to a specific legal contract. SOAP's standardization performs wonderfully, allowing the terms of the contract to be formally codified throughout the API's processing.

😩 Cons

The standardization of SOAP makes requests incredibly accessible to applications, but as a side effect, the format can become very verbose. Each message must include an envelope tag at the beginning and end, a body that contains the actual request, a header for specific information and additional requirements, and any errors that occur during processing.

In recent years, SOAP has declined in popularity due to the sheer amount of information it requires. The XML files are often unnecessarily bulky, especially for simple systems. The number of people who specialize in SOAP servers is shrinking rapidly, making it difficult to maintain them if you don't already have the right talent on your team.

GraphQL

💪 Pros

GraphQL API queries are well-documented, giving users all the information they need to use them effectively. The precise results, detailed error messages, and flexible permissions make for balanced and highly functional APIs. This is especially true when it comes to data structuring, where GraphQL gives users significant flexibility.

😩 Cons

GraphQL suffers from performance issues if you have too many nested fields in a request. It also doesn't reuse standard HTTP caching semantics, so it requires custom effort to achieve proper caching, making it difficult to learn without a lot of training and experience.

gRPC

💪 Pros

It's simple, use GET to get information and POST for everything else. This means that functions are easy to add, and you get great overall performance for lightweight payloads. The ability to define any type of function makes it infinitely configurable.

By simplifying otherwise complex remote calls, gRPC has also become a staple of the Docker-based application world, proving its value when you need to make large numbers of remote calls.

😩 Cons

gRPC is tightly coupled to the underlying system, which limits its reusability in many cases. In addition, there is no abstraction layer between the API and the actual system functions, which can raise security concerns.

WebSockets

💪 Pros

WebSockets act as a light transport layer that sits on top of your TCP/IP technology stack. The API allows you to send messages to a server and receive event-driven responses without having to poll the server for a response.

😩 Cons

The inherent difference between a WebSockets API and a gRPC API is that WebSockets is based on HTTP/1.1 while gRPC was built on HTTP/2. It was a natural evolution of technology, but that's not to say that one is better than the other.

Afterword

In summary, REST APIs offer simplicity, scalability, and better integration capabilities because they rely on standard Web technologies. They also tend to have better performance and security options. However, traditional APIs still have their use cases and may be appropriate in scenarios where legacy systems or specific protocols are already in place.