API vs REST API: Differences with Examples

What is an API?

An API (Application Programming Interface) is a defined way for software components to communicate. It describes available operations, inputs, outputs, and rules. APIs can be local libraries, operating-system interfaces, database drivers, or network services.

For example, a payment provider may offer an API to create a payment, check its status, or issue a refund. The API contract tells developers which fields are required and what errors may occur.

What is a REST API?

REST (Representational State Transfer) is an architectural style for distributed systems. A REST-style web API commonly exposes resources through URLs and uses HTTP methods such as GET, POST, PUT, PATCH, and DELETE. It commonly exchanges JSON, but REST does not require JSON; representations can use other media types.

API vs REST API

Example: a product API

A REST-style service might provide the following endpoints:

GET    /api/products       # list products
GET    /api/products/42    # read product 42
POST   /api/products       # create a product
PATCH  /api/products/42    # update selected fields
DELETE /api/products/42    # delete product 42

A successful GET request might return:

{
  "id": 42,
  "name": "Keyboard",
  "price": 1499
}

The endpoint and JSON are examples only; a real API must document authentication, validation, pagination, error responses, and versioning decisions.

What makes an API RESTful?

REST is more than “JSON over HTTP.” Its commonly discussed constraints include client-server separation, stateless requests, cacheability where appropriate, a uniform interface, a layered system, and optional code-on-demand. Real-world APIs vary in how completely they follow these constraints, so “REST-style” can be more precise than claiming every HTTP API is fully RESTful.

When should you use a REST API?

• When a browser, mobile app, and other services need a broadly supported HTTP interface.
• When resources can be represented clearly and standard HTTP semantics fit the use case.
• When caching, proxies, and common developer tooling are useful.

Other approaches can fit better for specialized needs: GraphQL supports client-selected data shapes, WebSockets support ongoing two-way communication, and gRPC is useful for strongly typed service-to-service calls. These are not simply “better” or “worse”; requirements decide.

Security and design checklist

• Use HTTPS for traffic in transit.
• Authenticate callers and authorize every protected operation.
• Validate input and avoid exposing stack traces or secrets in errors.
• Use suitable status codes, pagination, rate limits, and monitoring.
• Document request/response schemas and breaking-change policy.

Frequently asked questions

Is every API a REST API?

No. REST is one architectural style; APIs also include libraries, RPC interfaces, GraphQL APIs, SOAP services, and more.

Does REST require JSON?

No. JSON is common, but REST does not mandate a single representation format.

Is an HTTP API automatically RESTful?

No. Using HTTP does not guarantee that an API follows REST constraints or uses HTTP semantics consistently.

What is an endpoint?

An endpoint is a network address or route through which an API operation can be reached, often a combination of a URL path and HTTP method.

What is the difference between API and endpoint?

An API is the overall interface or contract; an endpoint is one reachable operation or route within that interface.

Which is best for beginners?

Learn HTTP basics and build a small REST-style API first. It teaches methods, status codes, JSON, validation, and authentication fundamentals.

Learning tip: Try the examples in a test project before using them in production. Check official documentation for behavior that depends on a tool, database, or version.