What Is a REST API? The Most Common Way Apps Talk to Each Other
📷 Rodrigo Santos · Pexels✦ Key takeaways
- REST is a style for designing web APIs using the HTTP protocol and URL-addressed resources.
- The four core methods: GET to read, POST to create, PUT/PATCH to update, DELETE to remove.
- Responses are usually JSON with a status code that signals the request's result.
- REST is stateless: each request is independent and carries everything it needs.
A REST API (short for Representational State Transfer) is a set of agreed rules that lets two applications exchange data over the web. When the weather app on your phone shows the temperature, it usually requests it from a remote server through a REST API and receives the reply in a structured format. The idea is that everything is treated as a resource with a clear address (URL), such as /users/42 for user number 42.
REST is built on the web's own protocol (HTTP) and uses its standard methods to express what operation you want on a resource. That's what makes it simple and familiar to any web developer: the same mechanism a browser uses to open a page is the one an app uses to request data.
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The table below shows the four core methods and what they do:
| Method | Purpose | Example | Safe/idempotent |
|---|---|---|---|
| GET | Read data | Fetch a product list | Yes (changes nothing) |
| POST | Create a new item | Add a product | No |
| PUT / PATCH | Update an item | Update a product price | PUT is idempotent |
| DELETE | Remove an item | Delete a product | Idempotent |
After each request the server replies with a three-digit status code that summarizes the result: 200 success, 201 created, 400 bad request, 401 unauthorized, 404 not found, 500 server error. Memorizing these common codes saves you a lot of time understanding any problem.
One of REST's key principles is that it is stateless: the server does not remember your previous requests, so each request must carry everything it needs (such as an access token). This makes the service easier to scale because any server can answer any request without needing to know what came before. The reply usually comes as JSON because it is lightweight and easy for both humans and machines to read.
To make it concrete: a request GET https://api.example.com/products/10 means "give me product number 10", and the server replies 200 with the product's data as JSON. If the product doesn't exist it replies 404. This simplicity is how most modern web and mobile apps that integrate with external services are built.
Bottom line: a REST API isn't a complex technology but an elegant agreement to use the web tools that already exist — URLs, HTTP methods and status codes — to exchange data in a uniform way everyone understands.
Sources
Osama AbdelAal is the founder of Marifa, a digital-marketing and entrepreneurship expert and Hootsuite EMEA Ambassador. He oversees and reviews Marifa’s editorial content to ensure it is accurate, clear and genuinely valuable.