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A REST API (Representational State Transfer Application Programming Interface), also known as a RESTful API, is a web-based Application Programming Interface (API) that is heavily used to develop web services and mobile applications.
Before we delve into the details of RESTful APIs, we must first understand what an API is.
An API is a set of protocols and routines that enable different systems and applications to communicate with each other, without either developers or end users having to know how they’re implemented. By leveraging APIs, developers can easily and quickly create reusable web and software applications.
There are many different types of APIs to serve different use cases. REST APIs are widely used to build web-based APIs and are an important part of modern web development.
REST stands for "Representational State Transfer." It is an architectural style for building web services that provide a standardised way for different computer systems to communicate with each other over the internet. REST is based on a set of design principles, rather than a specific technology or protocol, and it is widely used in building web-based APIs.
One of the key features of REST is its use of HTTP methods such as GET, POST, PUT and DELETE to represent different operations that can be performed on resources. These resources can be any kind of data or functionality that is exposed by the web service, and they are typically represented using a standardised data format, usually JSON.
A REST API is stateless, meaning that each request from the client contains all the information necessary to complete the request, and the server does not store any client context between requests. This makes REST APIs flexible, scalable and easy to cache.
Like all other APIs, RESTful APIs work by providing a standardised way for different computer systems to communicate with each other over the internet. Specifically, REST APIs expose resources that third-party apps and services can access and manipulate using standard HTTP methods. These resources can be any kind of data or functionality that the API provides, such as user data, product information or search results.
To access a resource in a RESTful API, a client sends an HTTP request to a specific endpoint, which is a URL that identifies the resource. The request typically includes additional information such as parameters, headers, and a message body, depending on the type of request.
The server processes the request, and if the request is successful, it sends an HTTP response back to the client. This response typically includes a status code, which indicates whether the request was successful or not, and a message body, which contains the requested resource in a standardised format.
Because REST APIs are stateless, the server does not keep track of any client state between requests. Each individual client request contains all the information necessary to generate a response.
There are numerous benefits to using RESTful APIs for building web services and data-driven applications:
Scalable: RESTful APIs are designed to be scalable, meaning they can handle large numbers of requests and accommodate traffic spikes. They use a simple, lightweight architecture that makes it easy to add new features or resources without having to re-architect the entire system.
Flexible: RESTful APIs are flexible and can be used with a wide range of programming languages and technologies. They are not tied to any specific platform or language, which means they can be used by clients running on different operating systems and devices.
Easy to use: RESTful APIs are easy to use and can be accessed using standard HTTP methods, making them accessible to developers of all skill levels. They provide a standardised way for different systems to communicate with each other, which can help reduce development time, improve productivity and minimise time-to-market.
Stateless: The fact that RESTful APIs are stateless means they’re more reliable and easier to cache, which can help reduce latency and improve performance.
Security: RESTful APIs can be secured using a variety of techniques, such as SSL/TLS encryption and OAuth authentication. This helps ensure that the API is protected against unauthorised access and that client data is kept secure.
Here are some best practices for designing and implementing well-structured, robust RESTful APIs that are easy to use, reliable and secure.
Use HTTP methods correctly: Use the appropriate HTTP methods (GET, POST, PUT, PATCH, DELETE, etc.) to perform different operations on resources, as per the HTTP specification. For example, use GET to retrieve a resource, POST to create a new resource, PUT to update an existing resource and DELETE to delete a resource.
Use meaningful URLs: Use URLs that are easy to read and understand, and that provide a clear indication of the resource being accessed. Avoid cryptic or meaningless URLs that are difficult to remember or identify.
Use JSON as your data format: While RESTful APIs can accept and respond to API requests in multiple data formats, JSON is the de facto modern standard for sending and receiving API data. This is because decoding and encoding XML or plain text can be a real hassle, and some frameworks don’t even support these formats anymore.
Use nouns, not verbs, in endpoint URLs: In other words, use https://www.example.com/posts, not https://www.example.com/getPosts or https://www.example.com/createPost. This is because HTTP methods such as GET, POST, PUT, PATCH, and DELETE are already in verb form. Using a noun indicates what the endpoint actually generates.
Don’t get creative with response codes: Use standard HTTP response codes to indicate the status of a request, such as 200 for success, 404 for not found and 500 for server errors. This makes it easier for clients to understand the result of their requests and take appropriate action.
Document, document and document some more: Provide clear and detailed documentation for your API, including information about the available resources, their data formats and the supported operations. This makes it easier for developers to understand and use your API.
Implement versioning: This ensures that changes to the API do not break existing applications by forcing them to migrate to the new version.
Return error details in the response body: Developers will thank you if your API returns error details, including the affected field, in the JSON or response body. This greatly helps with debugging apps.
Secure your API: Implement security measures such as SSL/TLS encryption, rate limiting and client authentication controls to ensure that threat actors can’t manipulate your API or knock it offline in a DDoS attack.