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WordPress REST API Basics
Helena Ivanova
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WordPress REST API Basics

When you use an app on your phone, the app connects to the Internet and sends requests to the server. It retrieves the necessary data, interprets it, and sends it back to your app. This process is possible because of the APIs (Application Programming Interface), and REST API is one of the most popular out there. And in this article, we will talk about it.

Table of Contents

What Are APIs, and How Do They Work?

Let’s start by clarifying what an API is. It stands for Application Programming Interface, which is a set of principles and rules that allows one program or software component to communicate with another through requests (also known as commands) and responses. “Application” means something digital that does a specific task, and “Interface” is for communication. 

They are mostly used for client-server communication.

APIs in simple terms

Let’s take an example from a non-digital world that is mostly global nowadays. It means that we all know some general rules that help people from different countries to interact and understand some basics about each other intentions, even if we don’t speak the same verbal or non-verbal language.

We all know that if we greet a person, we don’t turn our backs on them but instead turn toward them, right? We wave, shake hands or bow. When we drive cars, there’s some understanding of lanes (forget some countries where people have special talents and don’t need them 😏). And all of us definitely know that if we come to the person and punch them in the face, it will not be a good conversation starter. 

I’ve just given the most primitive examples of what can be called the “universal code of conduct.” But in each country, we have our specific codes: in the UK, there is left-hand traffic; in Japan, people bow instead of shaking hands, etc. 

All these sets of regulations are sort of APIs, and their goal is to help us interact efficiently, avoid misunderstandings and get things done, just like REST API or WordPress API (which is all about making WordPress a solid thing). 

Don’t forget that programming languages are, first of all, languages, which means that their primary role is communication, so the message brought by an expression or a line of code should be interpreted correctly.

When someone invites us to a Zoom meeting, we can add this event in one click (or fully automatically) to the Google Calendar. Because they communicate well, and it’s one of the examples of great API “teamwork.” 

API Protocols

As I’ve already mentioned, just like different countries can have their own specific codex of rules, there can be different APIs for applications to communicate. And the most popular and efficient is the REST API, so here we are. But first, let me say a few words about other APIs.

So, if you and your friend want to have a set of secret signs to hint that you are done with a party (but other people shouldn’t be offended), why not? Big companies or SaaS developers also like the situation when no outsider knows what they send over the Internet and how their software works and interacts. That’s why Internal (only for the company), Partners (company and its friends), and Composite (some kinds of mixed) APIs exist.

But the most interesting category for us now is Open and Public APIs. They just want you to speak their language and are happy to give some documentation. We will talk about this category, and the RESTful API is the most popular and frequently used among them. 


Don’t mix up APIs and web protocols (such as HTTP, FTP, TCP/IP). Web protocols are strict sets of rules on how data is being transmitted over the Internet, while APIs are sets of regulations about how software applications can communicate with each other.
APIs use web protocols for communication, though.

Some alternatives to REST API

We will talk about REST API further, so let’s mention other protocols and architectures. They have their pros, cons, and specific use cases. The most popular are:

  • SOAP – it uses XML and is a bit more heavy and complicated than REST. 
  • WebSockets – used for applications that require real-time updates, such as chats or online gaming.
  • gRPC – known for performance and scalability, developed by Google and used mostly for microservices

API Endpoints

APIs use endpoints. Endpoints are URLs, the unique addresses for particular resources or operations within API. They are used with HTTP verbs (or request methods) to manipulate the data from those endpoints. Examples of such verbs are: GET, POST, PUT, DELETE, etc., and they are used to retrieve data from the server, upload data to the server, modify it, or delete. When you type any URL in the browser’s address bar, in most cases, you fire a GET request, your browser acts as a client, and the server sends it all the data you’ve requested. 

An example of an API request (method+the endpoint):


In this example, it sends a request about users, and the server will return us a list of the users. Of course, in real life, endpoints can be more specific to return something more specific.

What’s a REST API?

Out of all the different APIs, it has many advantages, such as flexibility, simplicity, scalability, caching, and other perks. REST API stands for “REpresentational State Transfer,” and it has a set of key principles or constraints that determine its architecture. It was created in 2000, so it’s sort of a young and aspiring thing.

6 REST API principles

These guiding principles actually explain why REST API is so popular: 

  1. Client-server. REST applications follow a client-server architecture where a server manages application data and state while a client handles user interactions. This clear separation of concerns allows for independent updates and improvements to each component.
  2. Stateless. Servers do not maintain client state, and clients manage their own application state. All the information required to process requests is included in the client’s requests to the server.
  3. Cacheable. The server must mark its responses as cacheable and non-cacheable. This allows systems and clients to cache responses for better performance and dispose of non-cacheable information to avoid using stale data.
  4. Uniform interface. The most well-known feature of REST is its emphasis on a uniform interface between components. So URLs and URIs have a standardized structure. 
  5. Layered system. Components in the system are confined to their respective layers and cannot see beyond them. It makes them hierarchical and leads to better security and performance. 
  6. Code on demand (optional). As a rule, the server sends pre-implemented code to the client, but it can also send it in the form of scripts or applets, so the client will deal with it in its way.

WordPress REST API and the use cases

WordPress REST API is not something different but just a set of implementations of REST API specifically for WordPress, its structure, and logic. It uses JSON to transfer data, and its main purpose is to deal with WordPress using external applications. 

REST API became a foundation for the Block Editor, and it’s one of the most promising ways to use REST because it gives a chance not to use PHP in theme development but go another way and even improve performance. 

If you want to check out how your website looks through the eyes of REST API, just add to the base URL /wp-json/wp/v2/posts/ to get something like And you will see your website’s posts.  

Let’s have a look at some examples of how REST API can be used in WordPress:

  • Distributing content from WordPress over different platforms: mobile or desktop applications, third-party services, and so on. 
  • Exchange data between two WordPress sites. 
  • Building custom front end using favorite JS technologies. 
  • Building a headless CMS and generating static sites.

💡 If you’re interested in exploring the power of custom WordPress API development for your unique projects, you can get connected to WordPress API development experts, and they will help you dive deep and understand more about WordPress API.

JetEngine REST API Feature

WordPress core has supported REST API since the 4.7 version. However, it’s basic functionality, and if you want to create custom endpoints, extend and modify the existing ones, and add some settings, you will need a plugin. 

JetEngine got you covered and includes the functionality such plugins have. Use CCT to work with REST API endpoints and manage data on your website using this API.


What is a REST API?

It is an Application Programming Interface that adheres to REST (or RESTful) principles.

What are the six guiding REST principles?

Uniform interface, statelessness, client-server architecture, layered system, code on demand, and cacheability.

What is a JSON?

JSON (JavaScript Object Notation) is an open standard file format that RESTful web services use.

Do I need to install WordPress REST API plugins to run REST API?

WordPress autonomous REST API system is fully functional. Third-party REST API plugins are emerging to expand their functionality and enhance UI.


REST API became the most commonly used type of API. Developers continue finding more ways REST API can extend WordPress functionality. It is obvious that in the nearest future, its role as a WordPress core building instrument will increase. For now, it is important to know that the REST API powers up WordPress and make it more flexible and universal.