Difference Between REST and RESTful APIs

REST stands for representational state transfer. It is a set of constraints that set out how an API (application programming interface) should work. If an API is RESTful, that simply means that the API adheres to the REST architecture. 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 Constraints Are Set Out By REST?

There are 4 main principles of REST as laid out by Roy Fielding and his colleagues in 2000. They set out to create a standard that allowed servers to communicate with other servers easily. This is what they came up with, changing the landscape of APIs:

1. Client-Server: There is always a client and a server, and these two systems need boundaries for how they operate. Which one is being called (server) and which one is making the request (client)? Having these boundaries leads to smoother operation.
2. Stateless: Servers need to be able to process messages they receive. In order to do this, every request a server receives should have the necessary information required for the server to work.
3. Uniform Interface: Using similar terminology and resources helps standardize APIs. According to this principle, the following HTTP verbs are used: GET, PUT, POST, and DELETE. Resources always refer to URIs (uniform resource identifier). HTTP responses always come with a status and a body.
4. Cacheable: Clients need to be able to cache representations. Because of statelessness (every representation being self-descriptive), this is possible in a RESTful API.

How Do You Know If Your API Is RESTful?

RESTful APIs are popular. After all, the whole reason behind REST was to standardize the web. Chances are, the APIs you work with or create will be RESTful to one degree or another. Some APIs are better than others at complying with the constraints set out by REST. You can view the documentation for a specific API to confirm whether or not it is RESTful.

Are There Other API Styles Besides REST?

Prior to 2000, APIs were the Wild West, and there were many different types. Since then, REST has risen in popularity, becoming somewhat of the go-to API style architecture. That being said, there are other API styles. SOAP (Simple Object Access Protocol) is another API style. Depending on what your project goals are, one API style might be better than another for you.