How to Use REST APIs – A Complete Beginner's Guide (2023)

/ #Rest Api
How to Use REST APIs – A Complete Beginner's Guide (1)
Alex Husar
How to Use REST APIs – A Complete Beginner's Guide (2)

Application programming interfaces – or APIs – are an important programming concept to understand. And if you invest the time to learn more about these interfaces, it can help make your tasks more manageable.

One of the common types of APIs is a REST API. If you’ve ever considered getting data from another website, such as Twitter or GitHub, you’ve probably used this kind of API.

So why is understanding a REST API useful? How does it ensure modern business connectivity?

Before building or operating an API, or a REST API in particular, you should first learn what an API is. This article will walk you through the REST API principles, and how they grew into powerful applications.

How Do APIs Work and Why Do You Need Them?

APIs represent a set of definitions and protocols. You need them for app development and integration as they facilitate data exchange between two pieces of software, like an information supplier (a server) and a user.

APIs specify the content available to the client making the call from the producer that's returning the response.

Programs use an API to communicate, retrieve information, or perform a function. APIs allow users to work with the system to return their desired result.

To put it simply, an API acts as a mediator between users (clients) and resources (servers).

When users make API requests or visit an online store, they expect a fast response. So you need to optimize Magento TTFB (Time To First Byte) or use other performance enhancement strategies that work best for your CMS.

The reasons to integrate an API include:

  • streamlining resource and information sharing
  • controlling who has access to what with the help of authentication and defining the rights
  • safety and control
  • no need to understand the software specifics
  • consistent communication between services, even though they use different technologies

Overview of REST APIs

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RESTful refers to software architecture which stands for “Representational State Transfer”. You may have heard of it in the context of standardizing the use of information exchange systems (web services).

These web services utilize a stateless protocol to make textual representations of their online resources available for reading and processing. A client performs well-known HTTP protocol-based activities like fetch, update, and delete.

REST was first established in 2000 with the goal of improving performance, scalability, and simplicity by enforcing specific limits on an API.

It has gained popularity because of the opportunity to cover various devices and applications. Below you will find some of the purposes of using REST APIs.

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1. Web Use

There’s no specific client-side technology for REST as it suits diverse projects, such as:

  • web development
  • iOS apps
  • IoT devices
  • Windows Phone apps

As you won’t have to stick to a specific client-side stack, you can build any infrastructure for your company.

(Video) APIs for Beginners - How to use an API (Full Course / Tutorial)

2. Applications in the Cloud

REST API calls are ideal for cloud applications due to their statelessness. If something goes wrong, you can re-deploy stateless components, and they can grow to manage traffic shifts.

3. Cloud Computing

An API connection to a service requires controlling how the URL is decoded. That’s why REST has become more useful in cloud services.

RESTful API architecture will become the norm in the future, thanks to cloud computing and microservices.

How do REST APIs Work?

Data (such as images, videos, and text) embody resources in REST. A client visits a specific URL and sends a server request to receive a response.

How to Use REST APIs – A Complete Beginner's Guide (5)

The Concept Behind REST APIs

A request (the URL you access) contains four components, which are:

  • the endpoint, which is the URL with the structure root-endpoint/?
  • the method with one of the five possible types (GET, POST, PUT, PATCH, DELETE)
  • the headers, serving various functions, including authentication and providing information about the content of the body (you can use the -H or --header option to send HTTP headers)
  • data (or body), that’s what you send to the server through the -d or --data option with POST, PUT, PATCH, or DELETE requests.

The HTTP requests allow you to operate with the database, such as:

  • POST request to create records
  • GET request to read or get a resource (a document or image, a collection of other resources) from the server
  • PUT and PATCH requests to update records
  • DELETE request to delete a resource from a server

These operations stand for four possible actions, known as CRUD: Create, Read, Update and Delete.

How to Use REST APIs – A Complete Beginner's Guide (6)

The server sends the data to the client in one of the following formats:

  • HTML
  • JSON (which is the most common one thanks to its independence of computer languages and accessibility by humans and machines)
  • XLT
  • PHP
  • Python
  • plain text

Why Use a REST API?

Why should you prefer REST over other APIs, such as SOAP? There are numerous reasons, like scalability, flexibility, portability, and independence.

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Not relying on the project structure

A separate client and server operation means that developers aren’t bound to any project parts. Thanks to adaptive REST APIs, they can develop each aspect without influencing another one.

Portability and adaptability

REST APIs work only when the data from one of the requests is successfully delivered. They allow you to migrate from one server to another and update the database at any moment.

Opportunity to scale the project in the future

As the client and server act independently, the coders may swiftly develop the product.

Features of the RESTful Architecture Style

Developers have to consider a rigid structure of some APIs, such as SOAP or XML-RPC. But REST APIs are different. They support a wide range of data types and may be written in practically any programming language.

The six REST architectural constraints are principles for designing the solution and are as follows:

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1. Uniform Interface (A Consistent User Interface)

This concept dictates that all API queries for the same resource, regardless of their origin, should be identical, that is, in one specific language. One uniform resource identification (URI) is associated with the same data, such as a user’s name or email address.

Another uniform interface principle states that messages should be self-descriptive. They must be comprehensible for the server to determine how to handle it (for example, the type of request, mime types, and so on).

2. Client-Server Separation

The REST architectural style takes a peculiar approach to the client and server implementations. The thing is, they can be done independently and don’t have to know about the other.

For example, the client has only the uniform resource identification (URI) of the requested resource and can’t communicate with the server program any other way. On the other hand, the server shouldn’t affect the client software. So it sends the essential data over HTTP.

What does this mean? You can modify the client code at any moment without impacting the server’s operation.

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The server code is in the same boat: changing the server’s side won’t affect the client’s operation.

You can keep client and server programs both modular and independent as long as each side knows what message format to deliver to the other.

What do we achieve by separating the user interface problems from the data storage constraints? We improve the interface flexibility across platforms and boost scalability.

Furthermore, each component benefits from the separation because it can evolve independently. A REST interface assists different clients in:

  • accessing the same REST endpoints
  • executing identical activities
  • receiving similar responses

3. Stateless Communication Between Clients and Servers

REST-based systems are stateless, meaning that the client state remains unknown to the server and vice versa. This constraint allows the server and the client to understand any sent message, even if they haven’t seen the preceding ones.

To enforce this constraint of statelessness, you need to use resources rather than commands. These are the nouns of the web. Their purpose is to describe any object you may want to keep or communicate to other services.

You can control, change, and reuse components without affecting the system as a whole, so the benefits of this constraint include achieving:

  • stability
  • speed
  • scalability of RESTful applications

Note that each request should include all the information required to complete it. Client applications have to save the session state since server apps shouldn’t store any data linked with a client request.

4. Cacheable Data

REST requires caching client-side or server-side resources wherever possible. Data and response caching are critical in today’s world because it results in better client-side performance.

How does it affect a user? Well-managed caching can reduce or eliminate some client-server interactions.

It also gives the server more scalability options due to the smaller burden on the server. Caching increases the page load speed and allows you to access previously viewed content without an Internet connection.

5. Layered System Architecture

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The RESTful layered design structure is the next constraint under discussion. This principle involves grouping different layers with specified functions.

The REST API layers have their responsibilities and come in hierarchical order. For example, one layer may be responsible for storing data on the server, the second for deploying the APIs on another server, and the third for authenticating requests in another server.

These layers act as mediators and prevent direct interaction between the client and server apps. As a result, a client doesn’t know which server or component they address.

What does it mean when each layer performs its function before transferring the data to the next? It improves the API’s overall security and flexibility because adding, altering, or removing APIs doesn’t affect other interface components.

6. On-Demand Coding (Non-obligatory)

The most common scenario of using REST APIs is to deliver static resource representations in XML or JSON.

However, this architectural style allows users to download and run code in the form of Java applets or scripts (such as JavaScript). For example, clients can retrieve the rendering code for UI widgets by calling your API.

Challenges You Should Expect When Using REST APIs

When you’ve understood REST API design and architectural constraints, you should know the issues to expect while employing this architectural style:

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Agreement on REST endpoints

APIs should remain consistent regardless of the URL construction. But with the growth of possible combinations of methods, it’s harder to maintain uniformity in large codebases.

(Video) What Is REST API? Examples And How To Use It

Versioning as a feature of REST APIs

APIs require regular updating or versioning to prevent issues with compatibility. However, old endpoints remain operational, which increases the workload.

A lot of authentication methods

You can specify what resources are available to what user types. For example, you can determine which third-party services can access customer email addresses or other sensitive information and what they can do with these variables.

But the 20 different authorization methods that exist can make your initial API call difficult. That’s why developers don’t proceed with the project due to the initial difficulties.

REST API security vulnerabilities

Although RESTful APIs have a layered structure, there still may be some security concerns. For example, if an application isn’t secure enough due to a lack of encryption, it can expose sensitive data.

Or a hacker may send thousands of API requests per second, causing a DDoS attack or other misuses of the API service to crash your server.

Excessive data collection and requests

A server may return a request with all the data, which may be unnecessary. Or you might need to run multiple queries to get the needed information.

Wrapping Up

There’s no surprise that APIs are predicted to streamline web-based communications in the future. Their purpose is to allow any web apps to interact and share data.

For example, they assist growing online businesses in developing robust and inventive systems. As the API architecture evolves, it adopts lighter and more flexible variants, which are critical for mobile apps and scattered networks.

So in this article you learned the basics of what you need to know about using REST APIs.






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Alex Husar

Chief technology officer at Onilab with 8+ years of experience in developing PWAs, Magento migration, and Salesforce development.

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How REST API works step by step? ›

Step #1 – Enter the URL of the API in the textbox of the tool. Step #2 – Select the HTTP method used for this API (GET, POST, PATCH, etc). Step #3 – Enter any headers if they are required in the Headers textbox. Step #4 – Pass the request body of the API in a key-value pair.

Is RESTful API easy to learn? ›

1) REST is Easy to Understand and Implement

REST is meant to work over HTTP (actually HTTP was influenced by REST). Therefore it makes use of HTTP verbs that most of us know, such as GET, POST, and PUT.

What is a REST API for dummies? ›

A RESTful API is an architectural style for an application program interface (API) that uses HTTP requests to access and use data. That data can be used to GET, PUT, POST and DELETE data types, which refers to the reading, updating, creating and deleting of operations concerning resources.

What are the 3 principles for a RESTful API? ›

REST design principles
  • Uniform interface. All API requests for the same resource should look the same, no matter where the request comes from. ...
  • Client-server decoupling. ...
  • Statelessness. ...
  • Cacheability. ...
  • Layered system architecture. ...
  • Code on demand (optional).
Apr 6, 2021

What is the difference between API and REST API? ›

An API, or application programming interface, is a set of rules that define how applications or devices can connect to and communicate with each other. A REST API is an API that conforms to the design principles of the REST, or representational state transfer architectural style.

What are the 5 principles for a RESTful API? ›

Principles of Rest API
  • Client-Server decoupling. In a REST API design, client and server programs must be independent. ...
  • Uniform Interface. All API queries for the same resource should look the same regardless of where they come from. ...
  • Statelessness. ...
  • Layered System architecture. ...
  • Cacheable. ...
  • Code on Demand.
Jan 18, 2023

What are the 4 most common REST API operations? ›

For REST APIs built on HTTP, the uniform interface includes using standard HTTP verbs to perform operations on resources. The most common operations are GET, POST, PUT, PATCH, and DELETE.

Is REST API just JSON? ›

The REST architecture allows API providers to deliver data in multiple formats such as plain text, HTML, XML, YAML, and JSON, which is one of its most loved features.

What should I learn before REST API? ›

  • Competitive Programming (Live)
  • Interview Preparation Course.
  • Data Structure & Algorithm-Self Paced(C++/JAVA)
  • Data Structures & Algorithms in Python.
  • Data Science (Live)
  • Full Stack Development with React & Node JS (Live)
  • GATE CS 2023 Test Series.
  • OS DBMS CN for SDE Interview Preparation.
Mar 31, 2021

What is difference between RESTful and REST API? ›

Put simply, there are no differences between REST and RESTful as far as APIs are concerned. REST is the set of constraints. RESTful refers to an API adhering to those constraints. It can be used in web services, applications, and software.

What should I know before learning REST API? ›

The Six Rules of REST APIs
  • Client-Server Separation. Under REST architecture, the client and server can only interact in one way: The client sends a request to the server, then the server sends a response back to the client. ...
  • Uniform Interface. ...
  • Stateless. ...
  • Layered System. ...
  • Cacheable. ...
  • Code on Demand (Optional)
Aug 30, 2022

What are the 3 types of APIs? ›

Today, there are three categories of API protocols or architectures: REST, RPC and SOAP.

What is REST API and how do you use it? ›

RESTful API is an interface that two computer systems use to exchange information securely over the internet. Most business applications have to communicate with other internal and third-party applications to perform various tasks.


REST API Commands
  • start.
  • stop.
  • pause.
  • resume.
  • details.
  • download.
  • redirect.
  • delete.

How long does it take to learn REST API? ›

You don't need much to get started, but you need to invest more than 3 hours. Just watching the content may not be enough to develop the skills needed. You need to do the work and the practice assignments.

How to learn REST API testing? ›

Steps to test RESTful API
  1. Open Advanced REST Client. Install Advanced REST Client. ...
  2. Enter the URL of the API you wish to test in the textbox.
  3. Select HTTP method in API testing, for example POST.
  4. Give Headers set in the Headers textbox. ...
  5. Click USE THIS SET.
  6. Provide body content. ...
  7. Submit the details to start testing.
Sep 22, 2021

Is REST API outdated? ›

The REST API will be alive for many years to come because many companies set up integrations and forget about them until there's a problem. It is still one of the dominant types of application integrations: REST API, SOAP, and more recently GraphQL. For those not, aware, REST is a type of API design pattern.

What is the main purpose of REST API? ›

RESTful API is an interface that two computer systems use to exchange information securely over the internet. Most business applications have to communicate with other internal and third-party applications to perform various tasks.

What is the 1st step in working with API? ›

The first step in creating an API is designing the API. You start by discovering what problems your API needs to solve, and then you determine what endpoints and data are needed. The decisions you make during the design phase must be documented somewhere.


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