REST API: Everything You Need to Know

Application Programming Interfaces (APIs) are everywhere, making it easy for all our apps and devices to work together smoothly and keep us updated with all the info we need.

At the most basic level, an API is a set of rules and protocols that lets one software application interact with another, and exchange data and functionalities easily and securely.

There are different types of APIs, but in this article, we’re going to talk about one type: the REST API.

In this blog post, we’ll take a deep dive into REST APIs, including the core principles, how they work, and some examples. We’ll also explain how to build and consume REST APIs, and take a look at some emerging trends and technologies affecting REST APIs.

REST definition: What does REST stand for?

REST – or Representational State Transfer – is an architectural style for designing networked applications.

It relies on a stateless, client-server, cacheable communications protocol – and in virtually all cases, it uses the HTTP requests to post data (create and/or update), read data (e.g., make queries), and delete data, mapping CRUD operations to HTTP methods.

By using standard HTTP methods such as GET, POST, PUT, and DELETE, REST APIs allow for interaction with web services in a straightforward and consistent way.

For example, to retrieve information from a resource, a developer might issue a GET request; to create a new record, a POST request; to update an existing record, a PUT or PATCH request; and to remove a record, a DELETE request.

REST APIs play a big role in the architecture of modern applications, especially for IoT and microservices. In the IoT ecosystem, REST APIs are crucial for enabling the communication between devices and the cloud, allowing for the remote control, monitoring, and management of devices.

In the world of microservices, REST APIs define the interfaces between different microservices, so they can work together as a cohesive application.

What is REST in simple words?

As someone who can appreciate the simplicity of things, here’s a definition of REST as framed for a 5-year-old:

Imagine you have a toy box at home filled with all kinds of toys. When you want to play with a specific toy, you ask your mom or dad, and they go to the box, find that toy, and give it to you.

Now, imagine if your toys could be anywhere in your house, not just in your toy box. To get a toy, you’d tell your mom or dad exactly where to find it, like “in the kitchen, under the table, behind the blue chair.” Then they go straight there, grab the toy, and bring it to you.

REST is like telling someone exactly where to find your toy so they can bring it to you quickly. It’s a way for computers and apps to talk to each other and say, “Hey, I need this piece of information, and it’s located right here.”

This makes it easy for them to share and receive information, just like getting your toys from wherever they are in the house!

How REST APIs Work

REST APIs operate on the principle of making standard HTTP requests to communicate between clients and servers.

At the heart of REST is the concept of resources, each uniquely identified by a URL. When a client wants to perform an action on a resource, it sends an HTTP request to the server’s URL associated with that resource, using one of the four main HTTP methods:

GET to retrieve data,
POST to create a new resource,
PUT or PATCH to update a resource, and
DELETE to remove a resource.

The server then processes this request and sends back an HTTP response, typically including a status code and, if applicable, the requested data in a format like JSON or XML.

This interaction is stateless, meaning every request must contain all the information the server needs to fulfill that request, without relying on any stored context from previous requests.

This design promotes scalability and independence across various components of a system, allowing REST APIs to seamlessly integrate with different languages and platforms.

Using HTTP’s existing infrastructure, REST APIs can use features like caching and authentication to enhance performance and security, making them a versatile tool in a developer’s arsenal for building scalable, efficient web services.

REST API Examples

Let’s dive into some straightforward examples to illustrate REST API calls. These examples will show basic operations using HTTP methods such as GET, POST, PUT, and DELETE.

GET Request

A GET request is used to retrieve data from a server. For example, if you want to get a list of users from an API, you might use a URL like this:

GET /api/users

This would return a list of users from the /api/users endpoint. The server responds with the data (usually in JSON or XML format) and a status code (e.g., 200 OK).

POST Request

A POST request is used to create a new resource on the server. For example, to create a new user, you might send a request like this:

POST /api/users
Content-Type: application-json

{
 "name": "Jane Doe", 
 "email":"[email protected]"
}

This request sends a JSON object containing the new user’s name and email to the /api/users endpoint, which processes the data and creates the new user.

PUT Request

A PUT request is used to update an existing resource. If you want to update a user’s information, you could use a PUT request like this:

PUT /api/users/1
Content-Type: application/json

{
 "name": "Jane Smith",
 "email": "[email protected]"
 }

This request would update the user with ID 1, changing their name and email to the new values provided in the request body.

DELETE Request

A DELETE request is used to remove a resource from the server. To delete a user with a specific ID, you could use a request similar to the following:

DELETE /api/users/1

This tells the server to delete the user with ID 1. If successful, the server might respond with a 204 No Content status, indicating that the action was completed but there’s no content to return.

Interacting with a REST API using tools like Postman or cURL simplifies the process of testing and debugging API endpoints.

With Postman, you can easily construct and send HTTP requests (GET, POST, PUT, DELETE, etc.) through a user-friendly interface, inspect the responses, and even automate tests.

You simply enter the URL of the API endpoint, choose the HTTP method, add headers (for instance, Content-Type: application/json), and, if necessary, include a request body with the data you’re sending or requesting.

In contrast, cURL offers a command-line approach, allowing you to execute API calls directly from the terminal or command prompt. A cURL command to create a new user might look like:

curl -X POST 
 -H "Content-Type: application/json" 
 -d '{"name":"John Doe", "email":"[email protected]"}' 
 http://api.example.com/users

Both tools are powerful for testing API endpoints. Postman offers a more graphical approach and cURL favors scriptable, command-line operations.

Building a REST API

Here’s an overview of the process and some crucial points to keep in mind regarding security, data formats, and documentation:

Design and planning

Start by identifying the resources (data entities) the API will expose, such as users, products, or services. For each resource, define the endpoints (URLs) and the HTTP methods (GET, POST, PUT, DELETE) that will be supported, aligning with the principles of REST for resource manipulation.

Implementation

Now it’s time to pick the programming language and framework that best suits your needs. Once you do that, design your data model to represent the resources identified during planning. Implement the logic for each endpoint, and check to see that the appropriate HTTP status codes are returned for different outcomes (success, client error, server error).

Key Considerations

Security: Use authentication (e.g., OAuth, API keys) to control access and HTTPS to encrypt data in transit. Consider adding rate limiting to prevent abuse and input validation to protect against SQL injection and other attacks.

Data format: While REST APIs can support multiple data formats, JSON is the most popular, because it’s lightweight and easy of use with JavaScript. However, you should also consider supporting XML if there’s a demand or if it suits your industry’s standards.
Documentation: Document every resource, endpoint, request type, expected input, and response format. Try using GenAI-powered tools like Swagger to automate and standardize the documentation.
Test it thoroughly: Use unit, integration, and functional tests to verify your API’s functionality, reliability, performance, and security. Over time, you’ll need to update your API to add features and improve performance.

Consuming REST APIs

Consuming REST APIs is a core skill for working on web applications, mobile apps, and other systems that rely on web-based services. By mastering this process, you can leverage a vast ecosystem of web services, extending the capabilities of your apps and integrating with third-party services and platforms.

Essentially, it’s all about an application acting as a client, interacting with a server’s API over the web using the HTTP protocol. To consume a REST API, you typically follow these steps:

Understand the API documentation: Before you can consume an API, you need to understand its structure, available resources, required request formats, and expected responses. This information is usually provided in the API’s documentation. Look for details like base URLs, endpoints for different resources, required headers (such as content-type or authentication details), and the data format (usually JSON or XML).
Make HTTP requests: Depending on your development environment, you’ll use different libraries or tools to make HTTP requests. Languages like JavaScript, Python, Java, and others have libraries or modules designed for HTTP communications. For example, JavaScript developers might use fetch or the axios library, while Python developers could use requests. Each request specifies an HTTP method (GET, POST, PUT, DELETE, etc.), the target URL (composed of the base URL provided by the API and the specific endpoint), any necessary headers, and, for methods like POST or PUT, a body containing the data to be sent.
Handle responses: After you make a request, your application will receive a response from the API that includes a status code indicating whether the request was successful (e.g., 200 OK, 404 Not Found, 500 Internal Server Error) and, for successful requests, the requested data in the specified format. Your application should parse this data (if necessary) and do something with it – display the data in the UI, process it or store it.
Error handling and debugging: It’s crucial to implement error handling to manage situations where the API doesn’t respond as expected. It might be because of network issues, errors in the request format, or problems on the server side. Handling errors the right way ensures your application can gracefully manage these issues.

Authentication Methods

Another consideration is authentication methods, which are crucial for securing access to REST APIs. Two widely adopted authentication methods are OAuth and API keys.

API Keys

API keys are simple alphanumeric codes that are passed along with HTTP requests, often as a header or query parameter. They serve as a rudimentary form of access control, identifying the calling application to the API. API keys are straightforward to implement and use, making them suitable for scenarios where the security requirements are not particularly stringent or complex.

But their simplicity is also a drawback: if an API key is exposed or stolen, the attacker gains access to the API with the same rights as the key’s owner. For this reason, API keys are best used along with other security measures or when the data you’re handling isn’t all that sensitive.

OAuth

OAuth is a more complex and secure authentication framework that enables applications to get limited access to user accounts on an HTTP service. It works by providing tokens instead of credentials to access data on other servers. OAuth is well-suited applications that perform actions on behalf of a user without needing credentials, like a third-party app requesting access to Facebook data.

OAuth 2.0, the most widely used version, simplifies the client-side flow and provides multiple “grant types” for different scenarios – authorization code for web applications, implicit for browser-based or mobile apps, and password for trusted apps. OAuth tokens can be scoped to limit access to specific types of data and can be revoked at any time, offering a more granular level of control and security compared to API keys.

Advantages of REST APIs

REST APIs are all about making life easier for developers who want to build cool stuff on the web without getting bogged down in complexity. They’re flexible, scalable, and pretty much ready to play ball with whatever you throw at them. Here are some key advantages:

Simple and user-friendly: REST plays nice with HTTP, which is like the universal language of the web. This means creating and working with REST APIs is pretty straightforward.
No sticky sessions: REST doesn’t cling to session info. Each request is its own island, carrying all it needs. This cuts down on server-side problems, making things simpler and providing the scalability to handle more visitors, if needed.
Plays well with others: REST doesn’t care about the technology or language your system speaks, as long as it uses HTTP. This makes it super easy to get different systems to talk to each other.
Web-friendly: Built on HTTP, REST feels right at home on the web. It can easily move through firewalls and other network barriers, making it a great choice for internet apps.
Flexible: While JSON is the go-to format for REST APIs (because it’s lightweight and easy to work with), REST can also work with XML or YAML, giving you the freedom to choose what works best for your project.
Easy to test: With REST using the familiar HTTP, testing and troubleshooting are less of a headache. There’s a ton of tools out there to help make sure everything’s working as it should.

Emerging Trends and Technologies Affecting REST APIs

The landscape of REST APIs is continually evolving. A significant trend is the adoption of HTTP/2 and HTTP/3, which offer improvements such as multiplexing and header compression to reduce latency and improving throughput.

Another trend is the increased use of API gateways and management platforms, which provide features like rate limiting, analytics, and security policies to help manage and scale API ecosystems efficiently.

The rise of serverless computing and function-as-a-service (FaaS) platforms enables scalable, event-driven architectures, so developers can focus on building and deploying API logic instead of worrying about the underlying infrastructure.

While REST is still a popular choice for web API design, GraphQL and gRPC address some of its shortcomings:

GraphQL eliminates REST’s over-fetching and under-fetching issues by allowing precise data queries, making it ideal for bandwidth-efficient and complex applications.
gRPC, based on Google’s Protocol Buffers, excels in high-performance, low-latency environments with support for bidirectional streaming, benefiting IoT and microservices communication.

Emerging technologies like GraphQL and gRPC offer specialized solutions for specific projects, however, REST APIs continue to be a smart choice for building flexible, interoperable web and mobile applications.

The Directus REST API

For those looking to leverage the power of REST (OR GraphQL) APIs within a modern, intuitive framework, check out Directus. Our REST API wraps your new or existing SQL database with a real-time API and an intuitive no-code app for non-technical users.

Take a look at our API Reference today to find out how we can help transform your data management and API strategies.