What is API vs API REST?

An API (Application Programming Interface) is a software interface that allows two applications to interact with each other by calling features and data from one application in another application. APIs allow different systems to communicate with each other in a fast and efficient way. There are different types of APIs, with two main categories being SOAP APIs and REST APIs.

A REST API is an API that follows specific architectural constraints in order to take advantage of the benefits of REST (REpresentational State Transfer) architecture. REST APIs use HTTP requests like GET, POST, PUT and DELETE to interface with other systems and exchange data through JSON or XML formats. REST principles encourage using straightforward URLs to locate resources and methods.

What is an API?

API stands for Application Programming Interface. An API is a software interface that enables two separate applications to interact with one another by exposing some of the application’s data and functionality for use by other developers. APIs allow different systems and applications to communicate with each other by calling various functions and features.

Some key characteristics of APIs include:

• Allow communication between two separate software applications
• Enable developers to access certain features or data from another application
• Written code containing functions, subroutines, protocols and tools for building software
• Act as an interface between separate software programs
• Enable seamless integration between systems and efficient data transfer

APIs are important because they allow different pieces of software to work together even if they are built on different platforms and languages. This enables innovative functionality and services by combining capabilities from multiple applications.

Some examples of common API use cases include:

• Social media apps use APIs to integrate user profile data from other platforms
• Travel booking sites use flight and hotel APIs to display available options and prices
• Marketplaces use payment APIs to process financial transactions
• Advertising platforms use analytics APIs to track campaign performance

Types of APIs

There are different types of APIs that are optimized for various use cases:

• Open APIs – Publicly available for any developer to use
• Partner APIs – Access given to select external partners
• Internal APIs – For communication within an organization
• Composite APIs – Combine multiple APIs into one interface

APIs can also be categorized by architecture style:

• SOAP APIs – Based on SOAP (Simple Object Access Protocol) with structured messaging
• REST APIs – Follow REST architectural constraints for scalability and performance

What is REST and RESTful API?

REST stands for Representational State Transfer. It is an architectural style for building scalable web APIs that take advantage of HTTP methods and protocols. A RESTful API is an API that follows REST principles and patterns to expose data and functionality through endpoints accessed over HTTP.

Here are some key principles of REST APIs:

• Client-server – Clear separation between client and server
• Stateless – No client context stored on server between requests
• Cacheable – Responses indicate if they can be cached
• Uniform interface – Resources exposed at endpoints with standard methods
• Layered system – Components can be independently modified

REST APIs expose various endpoints that can be accessed and manipulated using standard HTTP methods like GET, POST, PUT and DELETE. For example:

• GET – Retrieve a resource
• POST – Create a new resource
• PUT – Update an existing resource
• DELETE – Delete a resource

REST APIs transfer data in either JSON or XML formats. The endpoints and hierarchical structure of the API is predictable and easy to understand. This makes REST a scalable and flexible architecture for web APIs.

Benefits of REST APIs

There are many benefits to using a RESTful API architecture:

• Scalability – No state stored on server so easy to scale horizontally
• Flexibility – Multiple data formats (JSON, XML) and protocols supported
• Efficiency – Uses caching for high performance by default
• Simplicity – Straightforward architecture with standard HTTP methods
• Portability – API can be accessed from any device or platform
• Reliability – No need for proprietary SDKs, uses standard HTTP

Differences between API and REST API

While REST APIs are a type of API, there are some key differences between APIs in general and REST APIs more specifically:

API	REST API
General architecture for app communication	Specifically follows REST architectural constraints
Can use protocols like SOAP, XML-RPC	Always uses HTTP protocol
Supports different data formats	Usually JSON or XML data format
Method names can vary	Standard methods GET, POST, PUT, DELETE
Tight coupling between client and server	Loose coupling between client and server
Can be complex to develop and use	Simpler and more straightforward to use

In summary, all REST APIs are APIs, but not all APIs are REST APIs. REST APIs adhere to specific constraints and principles to create scalable and flexible web services.

REST API Example

Here is an example of a simple REST API that manages customer data. It demonstrates the core REST concepts:

• HTTP methods to manipulate data
• Structured endpoints for resources
• JSON formatted request and response

HTTP GET

Retrieve a list of customers:

Request:

GET /api/customers

Response:

HTTP 200 OK

[
  {
    "id": 1,
    "name": "John Doe",
    "email": "[email protected]"
  },
  {
    "id": 2,
    "name": "Jane Smith",  
    "email": "[email protected]"
  }
]

HTTP POST

Create a new customer:

Request:

POST /api/customers

{
  "name": "Bob Wilson",
  "email": "[email protected]" 
}

Response:

HTTP 201 Created

{
  "id": 3,  
  "name": "Bob Wilson",
  "email": "[email protected]"
}

HTTP PUT

Update an existing customer:

Request:

PUT /api/customers/3

{
  "name": "Robert Wilson" 
}

Response:

HTTP 200 OK

{
  "id": 3,
  "name": "Robert Wilson", 
  "email": "[email protected]"  
}

HTTP DELETE

Delete a customer:

Request:

DELETE /api/customers/3

Response:

HTTP 204 No Content

This example shows the core REST API concepts in action – using standard HTTP methods to manipulate resources at different endpoints and exchanging JSON data.

When to use REST vs other APIs

Here are some key considerations when deciding between using a REST API or another API architecture:

• Use REST for public-facing APIs when you want scalability
• Use REST for web-based applications communicating over HTTP
• Use SOAP for internal services that require formal contracts
• Use SOAP when you need to support complex transactions
• Use gRPC for low-latency internal microservices
• Use GraphQL for flexible queries when clients need specific fields
• Use MQTT for communication with IoT devices
• Use Webhooks for notification of events from one app to another

There are tradeoffs with each type of API. Evaluate requirements around use case, complexity, payload size, client devices, and more when selecting an API architecture.

Conclusion

APIs provide ways for different software applications to communicate with each other by exposing data and functionality. REST APIs are a specific kind of API that follows REST principles to focus on scalability and flexibility.

Key highlights include:

• REST uses standard HTTP methods and provides a uniform interface
• REST APIs expose structured endpoints and JSON/XML data
• REST avoids state on the server side so it can scale easily
• REST simplifies integration between systems and components
• When building web APIs, REST is often the best architecture

By leveraging REST principles, APIs become easy to use by a wide range of client devices. The REST architectural style has made APIs ubiquitous in connecting modern applications together over the internet.