What is REST API?
To understand REST API, it is important to first understand the concept of REST. REST is not a programming language or a framework. It is an architectural style that defines how systems operating over a network can be structured. In the REST approach, data and objects within a system are generally treated as resources.
For example:
/users — users
/products — products
/orders — orders
These resources are accessed through specific addresses, and different operations can be performed on them.
How Does REST API Work?
REST API mainly works based on the request and response principle. For example, a user opens a products page.
The Frontend may send a request to the server like this:
GET /products
The Backend receives the request, retrieves the required data from the database, and returns the response to the Frontend.
The response may often be in JSON format:
{
"id": 1,
"name": "Laptop",
"price": 1500
}
The Frontend receives this data and displays it to the user through an appropriate interface.
What Is a REST API Endpoint?
An endpoint is an address used to access a specific resource or operation within a REST API.
For example:
/products
/users
/orders
For a more specific resource, an endpoint like this may be used:
/products/15
Here, 15 may be the identifier of a specific product. Therefore, an endpoint shows which resource on the server we want to work with.
What Are GET, POST, PUT, PATCH, and DELETE?
REST APIs use HTTP methods to specify which operation should be performed on a resource.
GET — used to retrieve data.
GET /products
It may return a list of products.
POST — used to create new data or trigger a specific operation on the server.
POST /products
It may be used to create a new product.
PUT — used to completely replace the current representation of the target resource.
PATCH — used to modify only specific parts of a resource.
DELETE — used to delete a resource.
These methods have officially defined HTTP semantics. For example, GET retrieves data, PUT replaces a resource representation, PATCH makes partial changes, and DELETE removes a resource.
What Is the Difference Between REST API and API?
API is a broader concept. An API is a set of interfaces and rules that allows software applications to communicate with one another. REST API, on the other hand, is one specific architectural approach used to build APIs.
In other words:
API → a general concept
REST API → one of the approaches used to build APIs
All REST APIs are APIs, but not all APIs are based on the REST approach.
Are REST API and RESTful API the Same?
The terms “REST API” and “RESTful API” are often used interchangeably in practice. A RESTful API refers to an API designed according to REST architectural principles. For example, clearly representing resources through endpoints, handling requests in a stateless way, and using appropriate HTTP semantics are all associated with the REST approach.
What Is the Stateless Principle?
One of the important characteristics of REST is that communication between the client and server is stateless. This means that the server should be able to understand each new request without relying on previous requests. All information required to process the request should be included in that request. This approach can make it easier to scale systems and operate them across multiple servers.
What Is JSON in REST API?
JSON is widely used for data exchange in REST APIs. JSON is a format used to represent structured data in text form.
For example:
{
"name": "Aysel",
"email": "aysel@example.com"
}
The Backend can send this data to the Frontend through an API, or the Frontend can send data to the Backend in the same format. REST is not limited to JSON, but JSON is a very common choice in modern web applications.
What Are HTTP Status Codes?
A REST API can use HTTP status codes to indicate how the server processed a request.
For example:
200 OK — the request was completed successfully.
201 Created — a new resource was created.
204 No Content — the operation was successful, but there is no response body.
400 Bad Request — there is a problem with the request.
401 Unauthorized — authentication is required or the provided authentication is invalid.
403 Forbidden — the server understands the request but does not allow access.
404 Not Found — the requested resource could not be found.
500 Internal Server Error — an error occurred on the server side.
Status codes make it easier to understand the result of the process between the Frontend and Backend.
How Does REST API Work with a Database?
A REST API is not a database itself. The Backend receives requests through the API and, when necessary, works with databases such as SQL, PostgreSQL, MySQL, MongoDB, and others.
For example:
- The Frontend sends a GET /products request.
- The Backend receives the request.
- The Backend sends an SQL query to the PostgreSQL database.
- The database returns the products.
- The Backend converts the result into JSON format.
- The REST API sends the response back to the Frontend.
For this reason, REST API is closely related to Backend development and databases.
Which Frameworks Can Be Used to Build REST APIs?
REST APIs can be built with different programming languages and frameworks.
In the Python ecosystem:
In the Java ecosystem:
In the JavaScript ecosystem:
- Express.js
- NestJS
In the C# ecosystem:
- ASP.NET Core
Frameworks help organize processes such as routing, request and response handling, authentication, validation, and database integration in a more structured way.
How Is REST API Security Ensured?
Security is especially important when building a REST API. In practice, methods such as HTTPS, authentication and authorization mechanisms, tokens, access permissions, input validation, and rate limiting can be used. For example, if a user wants to access personal profile information, the server may first verify the user’s identity. Token-based authentication methods such as JWT are also widely used in web APIs.
Where Are REST APIs Used?
REST APIs are used in many areas where data exchange between different systems is required.
For example:
- web applications;
- mobile applications;
- e-commerce systems;
- payment platforms;
- social networks;
- map services;
- artificial intelligence applications;
- microservice architectures;
- integration of internal company systems.
For example, a mobile application may retrieve user information from the Backend through an API, or an online store may communicate with a payment system through an API.
What Do You Need to Know to Learn REST API?
For those who are starting to learn REST API, it is useful to first understand the concept of an API.
Then, the following topics can be learned:
- HTTP and HTTPS;
- request and response;
- endpoint;
- GET, POST, PUT, PATCH, and DELETE;
- JSON;
- HTTP status codes;
- authentication and authorization;
- SQL and databases;
- Backend frameworks.
After that, practical REST API projects can be built using technologies such as Python and Django REST Framework, Java and Spring Boot, or JavaScript and Express.js.
Why Is REST API Important for a Backend Developer?
One of the main responsibilities of a Backend Developer is to build the server-side logic of applications and enable different systems to work with data. A Frontend application, mobile application, or another service often communicates with the Backend through an API. For this reason, creating endpoints, working with HTTP methods, sending data in JSON format, connecting APIs with databases, and ensuring API security are important practical skills in Backend development.
Frequently Asked Questions
Is REST API a programming language?
No. REST API is not a programming language. REST APIs can be built with different programming languages and frameworks.
Are REST API and HTTP the same thing?
No. HTTP is a protocol used for data exchange over the web. REST is an architectural style. Web-based REST APIs are usually built on top of HTTP.
Are REST API and JSON the same thing?
No. REST API is an approach to organizing communication between software systems, while JSON is a format used to represent and transfer data.
Do you need to know SQL for REST API?
Not every REST API necessarily uses SQL. However, because many Backend applications work with databases, knowing SQL is highly useful in practice.
Is REST API necessary for Frontend development?
A Frontend Developer may not create APIs, but knowing how to work with REST APIs is very useful for retrieving data from and sending data to the Backend.
Which programming languages can be used to create a REST API?
REST APIs can be built with Python, Java, JavaScript/TypeScript, C#, PHP, and many other programming languages.
If you would also like to learn what an API is and explore other programming topics, join our Backend or Full-Stack courses!
https://jetacademy.az/en/courses/full-stack-development-course