What is a RESTful API?

Interested in knowing what a RESTful API is? In this article, we will explain what an API is and provide some details about the concept of RESTful APIs. Let's start.

If you want to click pictures using your smartphone's camera, you don‘t code an interface for the camera, rather you use their API.
If a website you visit asks for your location, it intends to use the geolocation API in your browser. APIs can control access to your hardware devices and software, and you can deny that request. This way, APIs also play an important role in security.

Read more about APIs in “What Is an API?”

So, what is a RESTful API? Let's see.

REST, i.e. REpresentational State Transfer is an architectural style. Roy Fielding had first come up with this concept in 2000. Read his dissertation on this architectural style for a detailed study.

This architectural style has its guiding constraints, which are as follows:

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’Client-Server‘: The user interface concern is separated from the data storage concern, which improves portability.
’Stateless': A request from the client to the server must have all the information to understand the request and can't depend on stored context information on the server.
’Cacheable‘: A response to a request must label data as ’cacheable‘ or ’non-cacheable‘.
’Uniform interface‘: Component interfaces are standardized following specific REST guidelines.
’Layered system‘: The REST architectural style makes use of hierarchical layers.
Optional ’Code on demand‘: Enables downloading the client functionality code as applets or scripts.

Read “What is REST” to know more about this architectural style. A REST API and a restful web service use this architectural style, and HTTP methods (HyperText Transfer Protocol) in API requests to create, read, update, and delete (CRUD) data.

You need to keep in mind that a RESTful API for a mobile app is a bit different from that for web apps. The differences are as follows:

While RESTful APIs communicate using HTTP in general, for mobile apps HTTPS, i.e. HyperText Transfer Protocol Secure comes into the picture. It's a form of HTTP, however, it's more secure, because it uses a secure socket layer (SSL). To know the difference, just check the website of your bank, and you will notice a green padlock sign at the top left of your browser. Read more about HTTPS in this Techopedia definition.
Mobile clients should do as little as possible, while servers should do most of the work.
Mobile app users are very demanding, hence, make sure you get a top-quality hosting solution, so you can avoid server issues.
You have seen the high frequency of mobile app updates, and you can expect the same for your apps too. Establish a robust version-control process, so you can manage the changes well.
Most mobile users expect that the app should offer at least a limited set of functionalities even when offline. However, when they are back online, they should see the database reconciled with their offline activities. You need to factor this into your API development project.

I hope my article satisfactorily answered your question of what is a RESTful API.

Planning to integrate RESTful APIs into your software products? Here are some statistics to support your plans. The global cloud API market size totaled $1,148.0 million in 2023, according to a report. The market is expected to reach $4,195.3 million by 2032 growing at a rate of 15.2% during 2024-2032.

You may need experienced software developers who have an in-depth understanding of RESTful API architecture, its development, testing, documentation, etc. to develop your API services securely and efficiently. Read our guide for details on how you can build a RESTful API for your mobile app to get an idea of API development.

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1. What is a RESTful API?

RESTful API is an application programming interface based on the REST architecture that enables the communication between client and server applications via RESTful web services.

2. What is REST?

REST stands for Representational State Transfer architecture that ensures flexible communication through a web API where data is not tied to the interface or methods. It follows a stateless protocol where client requests for communication with a server should have all the required information in request headers. The information can be in the form of JSON (javascript object notation), HTML, plain text, etc. HTTP requests contain information like metadata, authorization, uniform resource identifier, cookies, etc.

3. What is REST vs. SOAP?

REST is an architecture pattern for client-server interactions following the REST principles whereas SOAP (simple object access protocol) is a protocol. Read more differences between REST and SOAP here.