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RESTful Web API Design – A Comprehensive Guide

the design of web apis by apilayer

REST APIs have increased in popularity in the software development world in recent years. REST (Representational State Transfer) is an architectural style that enables data communication between applications and forms the basis of web-based services. RESTful Web API makes it easier for developers to share and interact with data across different platforms, while also enabling the development of modular and scalable software. Therefore, today many large companies and developer communities tend to develop their applications and manage their integration processes using REST APIs. At the same time, the importance of the design of Web APIs is increasing day by day.

RESTful Web APIs are increasingly important not only for developers but also for users and businesses. APIs provide a harmonious experience between applications because they provide a standard structure when exchanging data between different platforms. This makes it easier for users to use different applications more fluently and share data. By using REST APIs, businesses can improve customer experience, open up to new markets, and optimize business processes with data integration. In this context, it can be said that REST APIs have strategic importance in both the technology world and the business world. In this article, we will take a closer look at RESTful Web APIs, which are increasingly important, and their design as a best practice.

Diving Deep: Understanding APIs and RESTful Web Services

understanding apis and restful web services

API (Application Programming Interface) is an interface that allows software to communicate with other software. APIs facilitate the sharing of data and functionality between applications and thus enable the integration of different systems with each other. REST API is a popular API protocol.

REST API works mainly using REST architecture. It is an architectural style for web-based services and is based on the HTTP protocol. REST APIs allow clients (usually web browsers or other applications) to communicate with servers using various methods of the HTTP protocol.

Pick up API examples, uses, and challenges of a REST API.

HTTP methods are an important concept that forms the basis of REST APIs. REST APIs perform different operations using HTTP methods. For example, operations such as reading a resource with the GET method, creating a new resource with the POST method, updating a resource with the PUT method, and deleting a resource with the DELETE method can be performed. These HTTP methods enable REST APIs to support basic CRUD (Create, Read, Update, Delete) operations, thus providing a user-friendly structure for data management.

Exploring the Features of REST Architecture

REST is one of the most common API protocols preferred in modern software development processes today. It is an architectural style and has several important features. These features provide REST benefits such as flexibility, scalability, and performance.

Firstly, one of the most important features of REST is independent code implementation. This feature ensures that the connection between client and server is not tight. That is, the client and server may use different technologies and be developed independently of each other. Thus, developers make the software development process flexible and get the advantage of working with different teams simultaneously.

Another important feature of REST is that it is stateless. This ensures that each request is processed separately and independently on the server side. When the client requests the server, the server processes the request and sends the response; However, as a result of this process, the server does not store any state about the client. In conclusion, keeping this state management on the client side reduces unnecessary complexity in the system and increases scalability.

Resource caching stands out as another significant feature. REST can locally cache resources received from the server and easily use this cache for future requests. This reduces network traffic, eases server load, and improves response times. It provides a huge performance increase, especially for repetitive requests.

It is also important that REST is designed as a layered system. This feature ensures that the connection between client and server is not through a single layer. The client can access the server using different network layers in the background.

Finally, REST’s “Code on Demand” feature ensures that the client can execute codes sent from the server. This feature is often used in browser-based applications and allows the client to run dynamically generated pieces of code from the server.

The Design of Web APIs

the design of web apis

Frequent use of RESTful Web API has led to the need to design it effectively. In this section, we will talk about the best practices of a web API design.

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Simple URL Structure

It’s essential to keep the base URL of our API simple and easy to read. This makes the API easy to use for API consumers and results in easy adoption on platforms that don’t have a properly supported client library.

Here is an example of a good base URL:

Moreover, if we’re designing an API that provides real-time exchange rates, a good URL could be:

Naming Best Practices

Using a standardized format or common patterns for naming makes it easy for API users to discover functionality and guess names and meanings of common properties without referring to the API documentation constantly.

Here are some of the best naming practices:

Resources Should be Name

Always use nouns in API URLs for resources instead of verbs. We have HTTP methods to describe different functions of REST APIs, so we don’t need verbs in naming the resources. For example, if we’re developing a currency rate API, we could use ‘latest‘ for real-time exchange rates instead of ‘getLatestRates.’

Resources Should be Named in Plural

A good practice is to keep the resource name plural. Although it’s not a requirement, singular names can create confusion about whether we’re requesting a single resource or a list of resources. It’s also essential to keep the names of resources uniform across our API.

An example of a plural resource name is as follows:

Using a plural name (‘Wheels’) also eliminates the need to add all with the resource, such as:

Slash (/) Should Be Used to Specify Hierarchical Relationships

We can clearly show the structure between sources with square brackets and slash marks. The hierarchical structure reveals the relationships of resources. For example, a best practice hierarchical structure for products is as follows:

Products Resource:

Hyphen (-) Should be Used for Spaces or Multiple Words

Using hyphens (-) to improve the readability of URIs is a usage that directly increases readability. For our URIs to be read and interpreted more easily, we should use the hyphen (-) character in paths consisting of more than one word.

Lowercase Letters Should be Used in All Naming

Another best practice is using lowercase letters to name URI paths.

File Extensions Should Not be Used

Using file extensions in URIs can often be unnecessary and clutter-inducing. In this case, the use of file extensions is generally discouraged, especially in RESTful APIs. There are several reasons for this and these reasons should be taken into account in API design.

  • Unnecessary Complexity and Obscurity: When file extensions appear in URIs, this can create unnecessary complexity for users of the API. For example, a URI such as /users/{id}/orders.xml simply indicates that data is received in XML format, but this information is usually not directly required by the client.

  • Long URIs and the Need for Abbreviations: File extensions increase the length of URIs, which can cause problems for client applications or web browsers. Long URIs can also reduce readability and complicate software development processes.

For these reasons, clean and understandable URIs should be preferred in API design instead of the use of file extensions. For example, a URI such as /users/{id}/orders can represent the user’s orders and communicate with the correct data formats without the need for file extensions.


API versioning is a crucial part of API design and development. It involves creating different versions of an API for different purposes and use cases. Versioning enables API developers to update the API over time and ensures that existing projects aren’t affected by API changes. While developers use one API version in their existing projects, various API versions provide flexibility for future projects.

As an API developer, we can use a version as a query parameter or date. However, a good practice is to use it as a prefix to the resource, such as:

Use the Right HTTP Methods

HTTP methods are of great importance in API design, and using the right methods correctly is critical to the reliability and performance of the API. For example, let’s design an API that executes operations related to books and associate these operations with the correct HTTP methods:

Use the Right HTTP Status Codes

API Design - A person coding on laptop

When an API call or request is made, it is either successful or unsuccessful. In case of an unsuccessful response, API developers need to show the correct HTTP status code to the users, such as whether the request was successful, an error occurred, or any further action is required. These responses are crucial to the proper outcome and working of the API.

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Here are the most common HTTP response or status codes:

  • 200: Operation/request was successful/ successful response

  • 201: New resource created successfully.

  • 204: Empty resource.

  • 400: Invalid request.

  • 401: Authentication is required.

  • 405: Invalid or incorrect HTTP method.

  • 415: Media/content type unsupported.

  • 429: Too many requests made by the user

  • 500-599: Server-side errors

Asynchronous operations

Sometimes an HTTP request, such as a GET or POST request, can require some time to process. In such a case, it’s best to make the operation asynchronous. For example, we can return the 202 HTTP status code, which means the request is accepted but is currently processing.

Data Limits and Pagination

Another crucial aspect of a good REST API design is using pagination and data limits. This is especially required for APIs that might return a large data set in response to a user request. If we don’t implement a mechanism for load balancing, the user can bring down the service. Using pagination and data limits, API developers can ensure not all requested data is sent in a single request.

Using pagination, API developers can split huge data into multiple smaller chunks or pages. With data limits, we can ensure that users only request and receive data within a certain limit. A good API design practice is to set a default data limit and offset.

Define Data Formats

Choosing the right request and response data formats is also essential to a good API design. A well-designed API uses JSON data format to return data. JSON is a lightweight modern-day data format that is human-readable and easy to parse. Additionally, the response body should include a descriptive message or error message and error codes if there is an error.

Implement User Authorization and Authentication Mechanisms

User authorization and authentication are crucial for data protection and security purposes and are essential for good API design. Authorization helps limit access permissions due to security concerns, whereas authentication helps ensure that only authenticated users can access the API and its data.

RESTful APIs typically make use of an API key to authenticate and identify a user. However, API producers must also implement advanced authorization and authentication techniques like the OAuth protocol. We should also focus on access control, validations, HTTP headers, and session management.

Detailed API Documentation

Many developers don’t focus on API documentation. However, extensive API documentation is essential for good API design. Good documentation includes all the details about API endpoints, methods, parameters, functionality, and responses. Additionally, it should include coding examples in various programming languages to ease the process of API integration. Here is an example of good API documentation.


To sum up, with the increasing importance of REST APIs, it is very important to design these APIs well and use them correctly. A well-designed REST API is more understandable and easy to use for users and provides a more flexible and extensible structure for developers. Factors such as using correct HTTP methods, clean URL structures, determining data formats, and taking security measures ensure the successful use of REST APIs. Additionally, a well-designed REST API speeds up development processes, facilitates data integration, and places inter-application communication on a more solid foundation. For these reasons, designing REST APIs well brings many advantages for both users and developers and plays an important role in modern software development processes.

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Frequently Asked Questions (FAQs)

Q: What is the RESTful Web API?

A: RESTful Web APIs are web services that are based on the principles of Representational State Transfer and communicate over the HTTP protocol. Such APIs work with resources and provide access to these resources using HTTP methods (GET, POST, PUT, DELETE, etc.). RESTful Web APIs generally use data formats such as JSON or XML and are widely preferred for developing extensible, scalable, and reliable applications.

Q: Why should I design my REST API well?

A: It is important to design REST APIs well because a properly designed API provides a number of benefits for users and developers. A good design makes the API easy to understand, use, and extend. Additionally, good design increases the performance, security, and scalability of the API. Factors such as using correct HTTP methods, clean URL structures, determining data formats, and taking security measures ensure successful use of the API.

Q: What is the difference between REST API and SOAP?

A: The main difference between REST API and SOAP is their communication protocols. While SOAP (Simple Object Access Protocol) is an XML-based protocol, REST (Representational State Transfer) operates over the HTTP protocol and usually uses data formats such as JSON or XML. While SOAP is generally known for its heavy structure, REST has a lighter and flexible structure. The fact that REST is stateless is also an important feature that distinguishes it from SOAP; This enables REST to find wider use and makes it the architecture of choice for modern web applications.

Q: How do we design an API?

A: Designing an API involves creating an API base URL and URI, naming API resources and properties, creating API endpoints, using the correct HTTP methods and response codes, creating API documentation, and more.

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