What is REST API?

A REST API (Representational State Transfer Application Programming Interface) is an architectural style and software interface that allows independent computer systems to communicate and exchange data over a network, typically the internet. In software engineering and data systems, an application programming interface establishes a standardized set of rules, protocols, and routing definitions that enable one software program to request services or information from another.

The "REST" designation indicates that the API adheres to a specific set of architectural constraints defined for distributed hypermedia systems. Rather than maintaining an open, continuous connection between systems, a REST API treats each communication interaction as an isolated request and response cycle. It models network functionalities as accessible resources, which are identified by unique URLs. When a client application queries a REST API, the server transfers a structured digital representation of the target resource's current state back to the client, usually formatted in standardized machine-readable data structures such as JSON or XML.

How does the communication mechanism of a REST API work?

The communication mechanism of a REST API relies fundamentally on the Hypertext Transfer Protocol (HTTP), the standard protocol for data transmission across the World Wide Web. When a client system requires data or needs to execute an operation on a remote server, it transmits an HTTP request to a designated URL known as an endpoint. This request comprises an HTTP method, header parameters specifying content types and authentication credentials, and an optional data payload containing parameters or records. The HTTP method explicitly defines the operational intent of the request: the GET method retrieves data from the server without altering it, the POST method submits new data to create a resource, the PUT or PATCH methods modify existing records; and the DELETE method removes specified resources. Upon receiving the request, the server processes the instructions, queries any associated databases or server-side logic, and returns an HTTP response. This response includes a three-digit numerical status code indicating execution success or failure (such as 200 for a successful operation or 404 for a missing resource) along with the requested data payload formatted according to the agreed serialization standard.

What is the difference between a REST API and a SOAP API or an RPC?

The primary distinction between a REST API and alternative web service technologies such as SOAP (Simple Object Access Protocol) or RPC (Remote Procedure Call) lies in their architectural design and data serialization requirements.

SOAP is a rigid, protocol-based standard that strictly requires XML for message structuring and relies on complex application-layer protocols for security and transaction compliance. This makes SOAP computationally intensive and increases network bandwidth consumption due to extensive XML metadata tags.

RPC frameworks, including modern variants like gRPC, are designed around executing specific functional actions or remote procedures rather than manipulating static data resources. In an RPC model, the client transmits a request to execute a specific remote function name with arguments, whereas in REST, the client interacts with a static noun-based resource identifier using standardized HTTP verbs.

REST APIs offer higher operational flexibility and lower latency in data-intensive applications because they natively support low-overhead JSON serialization, require minimal structural formatting, and utilize existing web infrastructure such as HTTP caching mechanisms without requiring specialized messaging protocols.