REST is an architectural style for designing networked systems, while a RESTful API is an API that actually follows REST’s constraints. In other words, REST is the set of rules, and “RESTful” describes an API that obeys them. Most APIs people call “REST APIs” follow some of those rules, like using resources and HTTP methods, but very few are fully RESTful in the strict sense Roy Fielding defined.

Sit in on enough API design reviews and you’ll hear it: “Is this endpoint RESTful?” Someone points out that POST /getUserOrders feels wrong. Someone else says it works fine, so who cares? Then a third person mentions HATEOAS, and half the room quietly opens a browser tab.

The confusion is understandable. Search for “REST vs RESTful” and you’ll find articles claiming RESTful APIs use less bandwidth, follow MVC, or are less secure. None of that is true. The real difference is simpler, and once you see it, it changes how you design APIs. In this guide, we’ll explain REST and RESTful APIs the way Fielding defined them, show code at each level of “RESTfulness,” and share practical design rules our team uses in API and backend development.

REST vs RESTful API at a Glance

What Is REST?

REST, short for Representational State Transfer, is an architectural style for distributed systems that defines a set of constraints for how clients and servers communicate, introduced by Roy Fielding in his 2000 doctoral dissertation.

Fielding wasn’t inventing a new technology. He was describing the principles that made the web itself scale so well, and he was one of the principal authors of the HTTP specification. You can read the original definition in Chapter 5 of Fielding’s dissertation.

The key idea is that everything is a resource, like a user, an order, or a product, identified by a URL. Clients don’t call functions on the server. They exchange representations of resources, usually JSON today, and change the state of those resources using a small set of standard operations.

The 6 REST Constraints

To be RESTful, an API must follow these architectural constraints:

The Uniform Interface, Explained

The uniform interface is the constraint that most separates REST from other approaches, and it has four parts:

1. Identification of resources: each resource has its own URL, such as /orders/123.
2. Manipulation through representations: clients change resources by sending representations, like a JSON body.
3. Self-descriptive messages: each message carries enough information, such as the HTTP method, headers, and media type, to be understood on its own.
4. Hypermedia as the engine of application state (HATEOAS): responses include links that tell the client what it can do next.

That fourth one is where most APIs fall short.

What Is a RESTful API?

A RESTful API is a web API that conforms to REST’s architectural constraints, exposing resources at URLs and letting clients work with them through standard HTTP methods, status codes, and representations.

In everyday conversation, “REST API” and “RESTful API” are used to mean the same thing: an HTTP API organized around resources. Strictly speaking, though, an API is only RESTful if it meets all of REST’s required constraints, including hypermedia.

Fielding himself made this point bluntly in a 2008 post titled REST APIs must be hypertext-driven, arguing that many APIs calling themselves REST weren’t REST at all.

Is REST API and RESTful API the Same?

In everyday practice, yes. Most developers use “REST API” and “RESTful API” interchangeably to mean an HTTP API built around resources. Technically, no. “REST” is the architectural style, and “RESTful” describes an API that fully follows it.

A useful way to remember it: every truly RESTful API is a REST API, but not every API called a “REST API” is truly RESTful.

The Real Difference Between REST and RESTful APIs

Here’s what actually separates a “REST-ish” API from a RESTful one. Notice that bandwidth, security, data formats, and MVC have nothing to do with it.

The Richardson Maturity Model: How RESTful Is Your API?

The Richardson Maturity Model, popularized by Martin Fowler, describes four levels of REST maturity, from plain remote calls over HTTP (Level 0) to fully hypermedia-driven APIs (Level 3).

Martin Fowler’s explanation of the Richardson Maturity Model is the clearest guide to how “RESTful” an API really is. Here’s what each level looks like in practice.

Level 0: One Endpoint, RPC Over HTTP

Everything goes to a single URL, usually with POST, and the action is in the body.

POST /api

{ “action”: “getOrder”, “orderId”: 123 }

Level 1: Resources

Each resource gets its own URL, but HTTP methods are still used loosely.

POST /orders/123/cancel

Level 2: HTTP Methods and Status Codes

Resources plus proper HTTP methods and status codes. This is where most “REST APIs” live today.

GET /orders/123

→ 200 OK

DELETE /orders/123

→ 204 No Content

Level 3: Hypermedia Controls (HATEOAS)

Responses tell the client what it can do next, so the client follows links instead of hard-coding URLs.

{

  “id”: 123,

  “status”: “pending”,

  “total”: 49.99,

  “_links”: {

    “self”:   { “href”: “/orders/123” },

    “cancel”: { “href”: “/orders/123”, “method”: “DELETE” },

    “pay”:    { “href”: “/orders/123/payment”, “method”: “POST” }

  }

}

If the order were already paid, the pay link simply wouldn’t appear. The server guides the client through valid actions, which is exactly what Fielding meant by hypermedia as the engine of application state.

HTTP Methods in RESTful APIs

RESTful APIs use HTTP methods according to their defined meaning in RFC 9110, the HTTP Semantics standard.

Safe means the request doesn’t change anything on the server. Idempotent means sending the same request once or ten times has the same effect, which matters a lot when networks retry failed requests.

Common HTTP Status Codes in REST APIs

Is Your API Really RESTful? A Quick Checklist

• Are your URLs nouns, not verbs? /orders/123, not /getOrder?id=123.
• Do you use the right HTTP method for each action? No GET requests that delete data.
• Is every request stateless? Authentication travels with each request, usually as a token, not a server-side session.
• Do you return meaningful status codes? Not 200 OK with “error”: true in the body.
• Do responses state their cacheability? Using headers like Cache-Control and ETag.
• Do responses include links to related resources and next actions? If not, you’re at Level 2, which is fine for many APIs, but not strictly RESTful.

Statelessness is the one that trips teams up most, especially around login. Our guide to web app session management explains how token-based authentication keeps APIs stateless without hurting security.

Should Your API Be Fully RESTful?

Honestly? Not always. Level 2 is the pragmatic sweet spot for most internal APIs and mobile app backends. You get predictable URLs, correct HTTP semantics, caching, and easy documentation with tools like OpenAPI.

Going to Level 3 with hypermedia makes the most sense when:

• Your API is public and long-lived, and you want clients to keep working as URLs and workflows change.
• Your workflows have many states, like orders, claims, or approvals, where available actions depend on the current state.
• You have many independent clients you don’t control.

The important thing is to be honest about what you’ve built. Calling a Level 2 API “REST” is fine and common. Calling an RPC-style Level 0 API “RESTful” just confuses everyone.

REST vs SOAP vs GraphQL vs gRPC

REST isn’t the only way to build APIs. Here’s how it compares with the other major styles.

Many modern systems mix them: REST for public APIs, gRPC between internal services, and GraphQL for data-heavy front ends.

RESTful API Design Best Practices

1. Use nouns and plural resource names: /users, /users/42/orders.
2. Version your API: in the URL (/v1/) or headers, so changes don’t break clients.
3. Paginate large collections: with limit and cursor or page parameters.
4. Support filtering and sorting through query parameters: /orders?status=paid&sort=-created_at.
5. Return consistent error objects: with a code, message, and details.
6. Use caching headers: Cache-Control and ETag reduce load and speed up clients.
7. Make retries safe: support idempotency keys for POST requests like payments.
8. Secure everything: HTTPS only, token-based auth, rate limiting, and input validation.
9. Document with OpenAPI: so developers and tools can generate clients and tests.
10. Monitor in production: track latency, error rates, and slow endpoints per route.

Building RESTful APIs in Practice

Every major backend stack builds RESTful APIs well, from Express and NestJS in Node.js to Django REST Framework and FastAPI in Python. Our guide to the best backend frameworks in 2026 compares the main options.

If your team works in JavaScript or TypeScript, you can hire Node.js developers who build REST APIs with Express or NestJS every day.

For Python teams, frameworks like FastAPI generate OpenAPI documentation automatically, and you can hire Python developers experienced in designing clean, versioned APIs.

Not every product needs a custom API from day one. Backend-as-a-service platforms can cover early needs, and our comparison of Firebase vs a custom backend explains when to switch to your own RESTful API.

Finally, the API is only one layer of the product. Our web application development team designs the API, front end, and infrastructure together, so they fit from the start.

Conclusion

REST vs RESTful isn’t a choice between two technologies. REST is the architectural style, and a RESTful API is one that truly follows it. Most real-world APIs sit at Level 2 of the Richardson Maturity Model, using resources, HTTP methods, and status codes well, and that’s a perfectly good place for many products. The key is to understand the constraints, apply them deliberately, and be honest about where your API stands.

Planning a new API or cleaning up an existing one? Book a free consultation with The Apps Developers, and we’ll help you design APIs that are predictable, secure, and easy for every client to use.